Semiconductor device having layers including aluminum and semiconductor device package including same

An embodiment discloses a semiconductor device including a light emitting structure including a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer; a first electrode electrically connected with the first conductive semiconductor layer; and a second electrode electrically connected with the second conductive semiconductor layer, and a semiconductor device package including the same. The second conductive semiconductor layer includes a first surface on which the second electrode is disposed. The second conductive semiconductor layer has a ratio of a second shortest distance W2, which is a distance from the first surface to a second point, to a first shortest distance W1, which is a distance from the first surface to a first point, (W2:W1) ranging from 1:1.25 to 1:100. The first point is a point at which the second conductive semiconductor layer has the same aluminum composition as a well layer of the active layer closest to the second conductive semiconductor layer. The second point is a point at which the second conductive semiconductor layer has the same dopant composition as the aluminum composition.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

TECHNICAL FIELD

Embodiments relate to a semiconductor device and a semiconductor device package including the same.

BACKGROUND ART

Semiconductor devices including compounds such as GaN and AlGaN have many merits such as wide and adjustable band gap energy and thus may be variously used as light emitting devices, light receiving devices, various kinds of diodes, or the like.

In particular, light emitting devices using group III-V or II-VI compound semiconductors or light emitting devices such as a laser diode may implement various colors such as red, green, blue, and ultraviolet due to the development of thin film growth technology and device materials and may implement efficient white light rays by using fluorescent materials or combining colors. These light emitting devices also have advantages with respect to low power consumption, semi-permanent life span, fast response time, safety, and environmental friendliness, compared to conventional light sources such as a fluorescent lamp, an incandescent lamp, or the like.

In addition, when light receiving devices such as optical detectors or solar cells are produced using group III-V or II-VI compound semiconductors, an optical current may be generated by light absorption in various wavelength ranges through development of device materials. Thus, light may be used in various wavelength ranges from gamma rays to radio wavelength regions. Also, the light receiving devices have the advantages of fast response time, stability, environmental friendliness, and ease of adjustment of device materials and may be easily used to power control or microwave circuits or communication modules.

Accordingly, semiconductor devices are being extensively used in the transmission modules of optical communication means, light emitting diode backlights substituted for cold cathode fluorescence lamps (CCFL) forming the backlights of liquid crystal display (LCD) devices, white light emitting diode lamps to be substituted for fluorescent bulbs or incandescent bulbs, car headlights, traffic lights, and sensors for detecting gas or fire. In addition, semiconductor devices may also be extensively used in high-frequency application circuits or other power control devices and even communication modules.

In particular, a light emitting device that emits light in an ultraviolet wavelength range may be used for curing, medical, and sterilization purposes due to its curing or sterilizing action.

Recently, research on ultraviolet light emitting devices has been actively conducted, but the ultraviolet light emitting devices are difficult to implement vertically and also have decreased crystallinity during the substrate separation process.

DETAILED DESCRIPTION OF THE INVENTION

Technical Problem

An embodiment provides a vertical ultraviolet light emitting device.

An embodiment also provides a light emitting device having enhanced optical output power.

Problems to be solved in the embodiments are not limited thereto, and include the following technical solutions and objectives of effects understandable from the embodiments.

Technical Solution

A semiconductor device according to an embodiment of the present invention includes a light emitting structure including a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer; a first electrode electrically connected with the first conductive semiconductor layer; and a second electrode electrically connected with the second conductive semiconductor layer. The second conductive semiconductor layer may include a first surface on which the second electrode is disposed. The second conductive semiconductor layer may have a ratio of a second shortest distance W2, which is a distance from the first surface to a second point, to a first shortest distance W1, which is a distance from the first surface to a first point, (W2:W1) ranging from 1:1.25 to 1:100. The first point may be a point at which the second conductive semiconductor layer has the same aluminum composition as a well layer of the active layer closest to the second conductive semiconductor layer. The second point may be a point at which the second conductive semiconductor layer has the same dopant composition as the same aluminum composition.

Advantageous Effects of the Invention

According to an embodiment, it is possible to produce a vertical ultraviolet light emitting device.

It is also possible to enhance optical output power.

Various advantageous merits and effects of the present invention are not limited to the above-descriptions and will be easily understood while embodiments of the present invention are described in detail.

MODE OF THE INVENTION

The following embodiments may be modified or combined with each other, and the scope of the present invention is not limited to the embodiments.

Details described in a specific embodiment may be understood as descriptions associated with other embodiments unless otherwise stated or contradicted even if there is no description thereof in the other embodiments.

For example, when features of element A are described in a specific embodiment and features of element B are described in another embodiment, an embodiment in which element A and element B are combined with each other should be understood as falling within the scope of the present invention unless otherwise stated or contradicted even if not explicitly stated.

In the descriptions of embodiments, when an element is referred to as being over or under another element, the two elements may be in direct contact with each other, or one or more other elements may be disposed between the two elements. In addition, the term “over or under” used herein may represent a downward direction in addition to an upward direction with respect to one element.

Hereinafter, example embodiments will be described in detail with reference to the accompanying drawings so that they can be easily practiced by those skilled in the art.

A light emitting structure according to an embodiment of the present invention may output ultraviolet wavelength light. For example, the light emitting structure may output near-ultraviolet wavelength light (UV-A), far-ultraviolet wavelength light (UV-B), or deep-ultraviolet wavelength light (UV-C). The wavelength range may be determined by the aluminum composition of a light emitting structure120.

For example, the near-ultraviolet wavelength light (UV-A) may have wavelengths ranging from 320 nm to 420 nm, the far-ultraviolet wavelength light (UV-B) may have wavelengths ranging from 280 nm to 320 nm, and the deep-ultraviolet wavelength light (UV-C) may have wavelengths ranging from 100 nm to 280 nm.

FIG. 1is a conceptual diagram of a light emitting structure according to an embodiment of the present invention, andFIG. 2is a graph showing the aluminum composition of the semiconductor structure according to an embodiment of the present invention.

Referring toFIG. 1, a semiconductor device according to an embodiment includes a light emitting structure including a first conductive semiconductor layer124, a second conductive semiconductor layer127, and an active layer126disposed between the first conductive semiconductor layer124and the second conductive semiconductor layer127.

The first conductive semiconductor layer124may be made of a group III-V or group II-VI compound semiconductor and may be doped with a first dopant. The first conductive semiconductor layer124may be made of a material selected from among semiconductor materials having an empirical formula Inx1Aly1Ga1-x1-y1N (0≤x1≤1, 0≤y1≤1, and 0≤x1+y1≤1), for example, GaN, AlGaN, InGaN, InAlGaN, and so on. Also, the first dopant may be an n-type dopant such as Si, Ge, Sn, Se, and Te. When the first dopant is an n-type dopant, the first conductive semiconductor layer124doped with the first dopant may be an n-type semiconductor layer.

The active layer126is disposed between the first conductive semiconductor layer124and the second conductive semiconductor layer127. The active layer126is a layer in which electrons (or holes) injected through the first conductive semiconductor layer124are combined with holes (or electrons) injected through the second conductive semiconductor layer127. The active layer126may transition to a lower energy level due to recombination between an electron and a hole and generate light having an ultraviolet wavelength.

The active layer126may have, but is not limited to, any one of a single-well structure, a multi-well structure, a single-quantum-well structure, a multi-quantum-well (MQW) structure, a quantum dot structure, and a quantum wire structure.

The second conductive semiconductor layer127may be formed on the active layer126and may be made of a group III-V or group II-VI compound semiconductor. Also, the second conductive semiconductor layer127may be doped with a second dopant. The second conductive semiconductor layer127may be made of a semiconductor material having an empirical formula Inx5Aly2Ga1-x5-y2N (0≤x5≤1, 0≤y2≤1, and 0≤x5+y2≤1) or a material selected from among AlInN, AlGaAs, GaP, GaAs, GaAsP, and AlGaInP. When the second dopant is a p-type dopant such as Mg, Zn, Ca, Sr, and Ba, the second conductive semiconductor layer127doped with the second dopant may be a p-type semiconductor layer.

The second conductive semiconductor layer127may include a 2-1(second-prime) conductive semiconductor layer127a, a 2-2(second-double-prime) conductive semiconductor layer127b, and a 2-3(second-triple-prime) conductive semiconductor layer127c. The 2-1 conductive semiconductor layer127amay have a lower aluminum composition than the 2-2 conductive semiconductor layer127b.

An electron-blocking layer129may be disposed between the active layer126and the second conductive semiconductor layer127. The electron-blocking layer129may block electrons supplied from the first conductive semiconductor layer124from flowing out to the second conductive semiconductor layer127, thus increasing the probability that electrons and holes will be recombined with each other in the active layer126. The electron-blocking layer129may have a higher energy band gap than the active layer126and/or the second conductive semiconductor layer127.

The electron-blocking layer129may be made of a material selected from among semiconductor materials having an empirical formula Inx1Aly1Ga1-x1-y1N (0≤x1≤1, 0≤y1≤1, and 0≤x1+y1≤1), for example, AlGaN, InGaN, InAlGaN, and so on, but is not limited thereto. A first layer129bhaving a high aluminum composition and a second layer129ahaving a low aluminum composition may be alternately disposed in the electron-blocking layer129.

Referring toFIG. 2, the first conductive semiconductor layer124, a barrier layer126b, a well layer126a, the 2-1 conductive semiconductor layer127a, the 2-2 conductive semiconductor layer127b, and the 2-3 conductive semiconductor layer127cmay all contain aluminum. Accordingly, the first conductive semiconductor layer124, the barrier layer126b, the well layer126a, the 2-1 conductive semiconductor layer127a, the 2-2 conductive semiconductor layer127b, and the 2-3 conductive semiconductor layer127cmay all be made of AlGaN. However, the present invention is not limited thereto.

The electron-blocking layer129may have an aluminum composition ranging from 50% to 90%. The blocking layer129may have a plurality of first blocking layers129ahaving a relatively high aluminum composition and a plurality of second layers129ahaving a relatively low aluminum composition, which are alternately disposed therein. When the aluminum composition of the blocking layer129is less than 50%, an energy barrier for blocking electrons may be insufficient in height, and the blocking layer129may absorb light emitted from the active layer126. When the aluminum composition of the blocking layer129is greater than 90%, the electrical characteristics of the semiconductor device may deteriorate.

The electron-blocking layer129may include a 1-1 section129-1and a 1-2 section129-2. The 1-1 section129-1may have an aluminum composition increasing toward the blocking layer129. The aluminum composition of the 1-1 section129-1may range from 80% to 100%. That is, the 1-1 section129-1may be made of AlGaN or AIN. Alternatively, the 1-1 section129-1may be a superlattice layer in which AlGaN and AlN are alternately disposed.

The 1-1 section129-1may have a thickness ranging from about 0.1 nm to about 4 nm. When the 1-1 section129-1has a thickness less than 0.1 nm, it may not be possible to efficiently block the movement of electrons. When the 1-1 section129-1has a thickness greater than 4 nm, it may be possible to reduce an efficiency with which holes are injected into the active layer126.

The 1-2 section129-2may include an undoped section. The 1-2 section129-2may serve to prevent dopants from spreading from the second conductive semiconductor layer127to the active layer126.

The 2-2 conductive semiconductor layer127bmay have a thickness greater than 10 nm and less than 200 nm. For example, the thickness of the 2-2 conductive semiconductor layer127bmay be equal to 25 nm. When the thickness of the 2-2 conductive semiconductor layer127bis less than 10 nm, resistance increases in a horizontal direction, and thus it is possible to reduce electric current injection efficiency. When the thickness of the 2-2 conductive semiconductor layer127bis greater than 200 nm, resistance increases in a vertical direction, and thus it is possible to reduce electric current injection efficiency.

The 2-2 conductive semiconductor layer127bmay have a higher aluminum composition than the well layer126a. In order to generate ultraviolet light, the aluminum composition of the well layer126amay range from about 30% to about 70%. When the 2-2 conductive semiconductor layer127bhas a lower aluminum composition than the well layer126a, the 2-2 conductive semiconductor layer127babsorbs light, and thus it is possible to reduce light extraction efficiency. However, in order to prevent a deterioration in crystallinity of the light emitting structure, the present invention is not limited thereto. For example, in some sections, the 2-2 conductive semiconductor layer127bmay have a lower aluminum composition than the well layer126a.

The 2-2 conductive semiconductor layer127bmay have an aluminum composition greater than 40% and less than 80%. When the aluminum composition of the 2-2 conductive semiconductor layer127bis less than 40%, light may be absorbed. When the aluminum composition of the 2-2 conductive semiconductor layer127bis greater than 80%, electric current injection efficiency may deteriorate. For example, when the aluminum composition of the well layer126ais equal to 30%, the aluminum composition of the 2-2 conductive semiconductor layer127bmay be equal to 40%.

The 2-1 conductive semiconductor layer127amay have a lower aluminum composition than the well layer126a. When the 2-1 conductive semiconductor layer127ahas a higher aluminum composition than the well layer126a, the 2-1 conductive semiconductor layer127ais unable to be sufficiently ohmic with a p-ohmic electrode due to an increase in resistance therebetween, and thus it is possible to reduce electric current injection efficiency.

The 2-1 conductive semiconductor layer127amay have an aluminum composition greater than 1% and less than 50%. When the aluminum composition is greater than 50%, the 2-1 conductive semiconductor layer127amay be unable to be sufficiently ohmic with a p-ohmic electrode. When the aluminum composition is less that about 1%, the 2-1 conductive semiconductor layer127amay have a composition close to GaN and thus absorb light.

The 2-1 conductive semiconductor layer127amay have a thickness ranging from 1 nm to 30 nm or ranging from 1 nm to 10 nm. As described above, the 2-1 conductive semiconductor layer127ahas an aluminum composition low enough to be ohmic and thus may absorb ultraviolet light. Accordingly, it may be advantageous, in terms of optical output power, that the 2-1 conductive semiconductor layer127abe adjusted to be as thin as possible.

However, when the thickness of the 2-1 conductive semiconductor layer127ais controlled to be 1 nm or less, the 2-1 conductive semiconductor layer127amay not be disposed in some sections, and there may be a region in which the 2-2 conductive semiconductor layer127bis exposed outside the light emitting structure120. Also, when the thickness is greater than 30 nm, the absorbed quantity of light is so large that optical output power efficiency may decrease.

The 2-1 conductive semiconductor layer127amay have a smaller thickness than the 2-2 conductive semiconductor layer127b. A thickness ratio of the 2-2 conductive semiconductor layer127bto the 2-1 conductive semiconductor layer127amay range from 1.5:1 to 20:1. When the thickness ratio is less than 1.5:1, the 2-2 conductive semiconductor layer127bis so thin that the electric current injection efficiency may decrease. When the thickness ratio is greater than 20:1, the 2-1 conductive semiconductor layer127ais so thin that there may be a reduction in ohmic reliability.

The aluminum composition of the 2-2 conductive semiconductor layer127bmay decrease as the 2-2 conductive semiconductor layer127bgets farther away from the active layer126. Also, the aluminum composition of the 2-1 conductive semiconductor layer127amay decrease as the 2-1 conductive semiconductor layer127agets farther away from the active layer126.

In this case, the 2-1 conductive semiconductor layer127amay have a greater reduction in aluminum composition than the 2-2 conductive semiconductor layer127b. That is, the 2-1 conductive semiconductor layer127amay have a greater variation in aluminum composition in the direction of thickness than the 2-2 conductive semiconductor layer127b.

The 2-2 conductive semiconductor layer127bhas a greater thickness than the 2-1 conductive semiconductor layer127aand has a higher aluminum composition than the well layer126a. Accordingly, the 2-2 conductive semiconductor layer127bmay have a relatively gradual reduction in aluminum composition.

However, the 2-1 conductive semiconductor layer127ahas a small thickness and has a large variation in aluminum composition. Accordingly, the 2-1 conductive semiconductor layer127amay have a relatively high reduction in aluminum composition.

The 2-3 conductive semiconductor layer127cmay have a uniform aluminum composition. The 2-3 conductive semiconductor layer127cmay have a thickness ranging from 20 nm to 60 nm. The aluminum composition of the 2-3 conductive semiconductor layer127cmay range from 40% to 70%.

FIG. 3is a secondary ion mass spectrometry (SIMS) graph of a light emitting structure according to a first embodiment of the present invention, andFIG. 4is a partially enlarged view ofFIG. 3.

Referring toFIGS. 3 and 4, the light emitting structure may have an aluminum composition and a p-type impurity (Mg) composition changing as the thickness thereof decreases. The aluminum composition of the second conductive semiconductor layer127may decrease and the p-type impurity (Mg) composition of the second conductive semiconductor layer127may increase toward the surface thereof.

The second conductive semiconductor layer127may have a ratio of a second shortest distance W2, which is a distance between the surface (a first surface, which has a thickness of zero) and a second point P21, to a first shortest distance W1, which is a distance between the surface and a first point P11, (W2:W1) ranging from 1:1.25 to 1:100 or from 1:1.25 to 1:10.

When the ratio of the second shortest distance W2to the first shortest distance W1(W2:W1) is smaller than 1:1.25, the first shortest distance W1and the second shortest distance W2are so close that the aluminum composition may rapidly change. When the ratio W2:W1is greater than 1:100, the thickness of the second conductive semiconductor layer127is so great that the crystallinity of the second conductive semiconductor layer127may deteriorate or a stress applied toward a substrate may increase, thus causing a change in wavelength of light emitted from the active layer.

Here, the first point P11may be a point at which the second conductive semiconductor has the same aluminum composition as the well layer126a, which is a part of the active layer closest to the second conductive semiconductor. The range of the first point P11may be defined as a spectrum measured through SIMS. The range of the first point P11may be defined as a portion of the second conductive semiconductor layer having the same aluminum composition as the well layer of the active layer.

In order to measure the first point P11, a method of using the SIMS spectrum may be applied, but the present invention is not limited thereto. As another example, TEM and XRD measurement methods may be applied thereto. Simply, the first point P11may be defined through the SIMS spectrum.

The second point P21may be a point of the SIMS spectrum at which a spectrum for a dopant (e.g., Mg) of the second conductive semiconductor layer and a spectrum for aluminum intersect.

During the measurement, a unit of value for the dopant of the second conductive semiconductor layer may be different depending on the case. However, a boundary region between the 2-1 conductive semiconductor layer127aand the 2-2 conductive semiconductor layer127bmay be included in a range of a point at which a region including an inflection point for the aluminum composition of the second conductive semiconductor layer and a spectrum for the dopant of the second conductive semiconductor layer intersect. Accordingly, it is possible to measure the boundary region between the 2-1 conductive semiconductor layer127aand the 2-2 conductive semiconductor layer127band define a range thereof.

However, the present invention is not limited thereto, and the second point P21may be a point positioned within a region having an aluminum composition ranging from 5% to 55%. When the aluminum composition of the second point P21is less than 5%, the 2-1 conductive semiconductor layer127ais so thin that power consumption efficiency of the semiconductor may deteriorate. When the aluminum composition of the second point P21is greater than 55%, the 2-1 conductive semiconductor layer127ais so thick that light extraction efficiency may deteriorate. In this case, the aluminum composition of the second point P21may be smaller than that of the first point P11. For example, the aluminum composition of the second point P21may range from 40% to 70%.

For example, the first shortest distance W1may range from 25 nm to 100 nm, and the second shortest distance W2may range from 1 nm to 20 nm.

A ratio of a first difference H1between an average aluminum composition of the electron-blocking layer129and the aluminum composition of the first point P11and a second difference H2between an average aluminum composition of the electron-blocking layer129and the aluminum composition of the second point P21(H1:H2) may range from 1:1.2 to 1:10.

When the ratio of the first difference to the second difference (H1:H2) is less than 1:1.2, a change in aluminum composition of a section between the first point P11and the second point P21is slow and thus it is difficult to sufficiently decrease the aluminum composition of the contact layer. Also, when the ratio of the first difference to the second difference (H1:H2) is greater than 1:10, the change in aluminum composition is rapid and thus it is possible for there to be an increase in probability of absorption of light emitted from the active layer.

FIG. 5is a SIMS graph of a light emitting structure according to a second embodiment of the present invention,FIG. 6is a partially enlarged view ofFIG. 5,FIG. 7is a SIMS graph of a light emitting structure according to a third embodiment of the present invention, andFIG. 8is a partially enlarged view ofFIG. 7.

Even referring toFIGS. 5 to 8, it can be seen that the ratio of the second shortest distance W2to the first shortest distance W1ranges from 1:1.25 to 1:100 or from 1:1.25 to 1:10. For example, referring toFIG. 8, it can be seen that a first point P13and a second point P23are located very close to each other.

Also, it can be seen that the ratio of the first difference H1between the average aluminum composition of the electron-blocking layer129and the aluminum composition of the first points P12and P13and the second difference H2between the average aluminum composition of the electron-blocking layer129and the aluminum composition of the second points P22and P23(H1:H2) may range from 1:1.2 to 1:10.

When such a condition is satisfied, the aluminum composition of the surface of the second conductive semiconductor layer127may be adjusted to a range from 1% to 10%.

FIG. 9is a conceptual diagram of a semiconductor structure according to an embodiment of the present invention, andFIG. 10is a graph showing an aluminum composition of the semiconductor structure according to an embodiment of the present invention.

Referring toFIGS. 9 and 10, a semiconductor device according to an embodiment includes a semiconductor structure120including a first conductive semiconductor layer124, a second conductive semiconductor layer127, and an active layer126disposed between the first conductive semiconductor layer124and the second conductive semiconductor layer127.

The semiconductor structure120according to an embodiment of the present invention may output ultraviolet wavelength light. For example, the semiconductor structure120may output near-ultraviolet wavelength light (UV-A), far-ultraviolet wavelength light (UV-B), or deep-ultraviolet wavelength light (UV-C). The wavelength range may be determined by the aluminum composition of the semiconductor structure120.

For example, the near-ultraviolet wavelength light (UV-A) may have a wavelength ranging from 320 nm to 420 nm, the far-ultraviolet wavelength light (UV-B) may have a wavelength ranging from 280 nm to 320 nm, and the deep-ultraviolet wavelength light (UV-C) may have a wavelength ranging from 100 nm to 280 nm.

When the semiconductor structure120emits ultraviolet wavelength light, each semiconductor layer of the semiconductor structure120may include materials Inx1Aly1Ga1-x1-y1N (0≤x1≤1, 0<y1≤1, 0≤x1+y1≤1) containing aluminum. Here, the aluminum composition may be represented as a ratio of the atomic weight of Al to the total atomic weight including the atomic weight of In, the atomic weight of Ga, and the atomic weight of Al. For example, when the aluminum composition is 40%, the composition of Ga is 60%. That is, the material may be Al40Ga60N.

Also, in the description of the embodiments, a composition being low or high may be understood by a difference in composition % (and/or % point) of each semiconductor layer. For example, when a first semiconductor layer has an aluminum composition of 30% and a second conductive semiconductor layer has an aluminum composition of 60%, the aluminum composition of the second conductive semiconductor layer may be represented as being higher than that of the first semiconductor layer by 30%.

The first conductive semiconductor layer124may be made of a group III-V or group II-VI compound semiconductor and may be doped with a first dopant. The first conductive semiconductor layer124may be made of a material selected from among semiconductor materials having an empirical formula Inx1Aly1Ga1-x1-y1N (0≤x1≤1, 0<y1≤1, and 0≤x1+y1≤1), for example, AlGaN, AlN, InAlGaN, and so on. Also, the first dopant may be an n-type dopant such as Si, Ge, Sn, Se, and Te. When the first dopant is an n-type dopant, the first conductive semiconductor layer124doped with the first dopant may be an n-type semiconductor layer. However, the present invention is not limited thereto, and the first conductive semiconductor layer124may be a p-type semiconductor layer.

The first conductive semiconductor layer124may include a 1-1 conductive semiconductor layer124a, a 1-2 conductive semiconductor layer124c, and an intermediate layer124bdisposed between the 1-1 conductive semiconductor layer124aand the 1-2 conductive semiconductor layer124c.

The 1-1 conductive semiconductor layer124amay have an aluminum composition ranging from 50% to 80%. When the aluminum composition of the 1-1 conductive semiconductor layer124ais greater than 50%, it is possible to improve light extraction efficiency by decreasing an absorption rate of deep-ultraviolet wavelength light (UV-C) emitted from the active layer126. When the aluminum composition of the 1-1 conductive semiconductor layer124ais less than 80%, it is possible to secure electric current injection characteristics for the active layer126and electric current spreading characteristics in the 1-1 conductive semiconductor layer124a.

The 1-2 conductive semiconductor layer124cmay be disposed closer to the active layer126than the 1-1 conductive semiconductor layer124a. The 1-2 conductive semiconductor layer124cmay have a lower aluminum composition than the 1-1 conductive semiconductor layer124a.

When the semiconductor structure120emits deep-ultraviolet wavelength light (UV-C), the aluminum composition of the 1-2 conductive semiconductor layer124cmay range from 40% to 70%.

When the aluminum composition of the 1-2 conductive semiconductor layer124cis greater than or equal to 40%, it is possible to improve light extraction efficiency by decreasing an absorption rate of deep-ultraviolet wavelength light (UV-C) emitted from the active layer126. When the aluminum composition of the 1-2 conductive semiconductor layer124cis less than or equal to 70%, it is possible to secure electric current injection characteristics for the active layer126and electric current spreading characteristics in the 1-2 conductive semiconductor layer124c.

The 1-1 conductive semiconductor layer124aand the 1-2 conductive semiconductor layer124cmay have higher aluminum compositions than the well layer126a. Accordingly, when the active layer126emits ultraviolet wavelength light, it is possible to reduce the absorption rate of ultraviolet wavelength light in the semiconductor structure120.

Also, when the 1-2 conductive semiconductor layer124chas a higher aluminum composition than the 1-1 conductive semiconductor layer124a, it may be easy to extract light from the active layer126to the outside of the semiconductor structure120due to a difference in refractive index. Accordingly, it is possible to improve the light extraction efficiency of the semiconductor structure120.

The 1-2 conductive semiconductor layer124cmay be thinner than the 1-1 conductive semiconductor layer124a. The 1-1 conductive semiconductor layer124amay have a thickness greater than or equal to 130% of that of the 1-2 conductive semiconductor layer124c. According to such a configuration, the intermediate layer124bis disposed after the thickness of the 1-1 conductive semiconductor layer124a, which has a high aluminum composition, is sufficiently secured. Accordingly, it is possible to enhance the overall crystallinity of the semiconductor structure120.

The intermediate layer124bmay have a lower aluminum composition than the first conductive semiconductor layer124and the second conductive semiconductor layer127. During a laser lift-off (LLO) process for removing a growth substrate, the intermediate layer124bmay serve to absorb laser emitted to the semiconductor structure120to prevent damage to the active layer126. Accordingly, the semiconductor device according to an embodiment can prevent damage to the active layer126during the LLO process, thereby enhancing optical output power and electrical characteristics.

Also, when the intermediate layer124bis in contact with a first electrode, the intermediate layer124bmay have a lower aluminum composition than the 1-1 conductive semiconductor layer124aand the 1-2 semiconductor layer124cin order to decrease resistance between the intermediate layer124band the first electrode and thus secure electric current injection efficiency.

The thickness and aluminum composition of the intermediate layer124bmay be appropriately adjusted to absorb laser light emitted to the semiconductor structure120during the LLO process. Accordingly, the aluminum composition of the intermediate layer124bmay correspond to the wavelength of the laser light used during the LLO process.

When the LLO laser light has a wavelength ranging from 200 nm to 300 nm, the intermediate layer124bmay have an aluminum composition ranging from 30% to 70% and a thickness ranging from 1 nm to 10 nm.

For example, when the wavelength of the LLO laser light is smaller than 270 nm, the aluminum composition of the intermediate layer124bmay increase to correspond to the wavelength of the LLO laser light. For example, the aluminum composition of the intermediate layer124bmay increase to a range from 50% to 70%.

When the aluminum content of the intermediate layer124bis higher than that of the well layer126a, the intermediate layer124bmay be unable to absorb light emitted from the active layer126. Accordingly, it is possible to enhance light extraction efficiency. According to an embodiment of the present invention, LLO laser light may have a wavelength less than that of light emitted from the well layer126a. Accordingly, the intermediate layer124bmay have an appropriate aluminum composition such that the intermediate layer124babsorbs the LLO laser light but does not absorb light emitted from the well layer126a.

The intermediate layer124bmay include a first intermediate layer (not shown) having a lower aluminum composition than the first conductive semiconductor layer124and a second intermediate layer (not shown) having a higher aluminum composition than the first conductive semiconductor layer124. A plurality of first intermediate layers and a plurality of second intermediate layers may be alternately disposed.

The active layer126may be disposed between the first conductive semiconductor layer124and the second conductive semiconductor layer127. The active layer126may include a plurality of well layers126aand a plurality of barrier layers126b. The well layer126ais a layer in which first carriers (electrons or holes) injected through the first conductive semiconductor layer124are combined with second carriers (holes or electrons) injected through the second conductive semiconductor layer127. When first carriers (or second carriers) in a conduction band and second carriers (or first carriers) in a valence band are recombined in the well layer126aof the active layer126, light having a wavelength corresponding to a difference in energy level (an energy band gap) between the conduction band and the valence band of the well layer126amay be generated.

The active layer126may have, but is not limited to, any one of a single-well structure, a multi-well structure, a single-quantum-well structure, a multi-quantum-well (MQW) structure, a quantum dot structure, and a quantum wire structure.

The active layer126may include a plurality of well layers126aand a plurality of barrier layers126b. Each of the well layers126aand the barrier layers126bmay have an empirical formula Inx2Aly2Ga1-x2-y2N (0≤x2≤1, 0<y2≤1, and 0≤x2+y2≤1). The well layer126amay have a different aluminum composition depending on the light-emitting wavelength.

The second conductive semiconductor layer127may be formed on the active layer126and may be made of a group III-V or group II-VI compound semiconductor. Also, the second conductive semiconductor layer127may be doped with a second dopant.

The second conductive semiconductor layer127may be made of a semiconductor material having an empirical formula Inx5Aly2Ga1-x5-y2N (0≤x5≤1, 0<y2≤1, and 0≤x5+y2≤1) or a material selected from among AlInN, AlGaAs, GaP, GaAs, GaAsP, and AlGaInP.

When the second dopant is a p-type dopant such as Mg, Zn, Ca, Sr, and Ba, the second conductive semiconductor layer127doped with the second dopant may be a p-type semiconductor layer. However, the present invention is not limited thereto, and the second conductive semiconductor layer124may be an n-type semiconductor layer.

The second conductive semiconductor layer127may include a 2-1 conductive semiconductor layer127a, a 2-2 conductive semiconductor layer127b, and a 2-3 conductive semiconductor layer127c. The 2-1 conductive semiconductor layer127amay have a lower aluminum composition than the 2-2 conductive semiconductor layer127band the 2-3 conductive semiconductor layer127c.

A blocking layer129may be disposed between the active layer126and the second conductive semiconductor layer127. The blocking layer129may block electrons supplied from the first conductive semiconductor layer124from flowing out to the second conductive semiconductor layer127, thus increasing the probability that electrons and holes will be recombined with each other in the active layer126. The blocking layer129may have a higher energy band gap than the active layer126and/or the second conductive semiconductor layer127. The blocking layer129is doped with the second dopant, and thus may be defined as a partial region of the second conductive semiconductor layer127.

The blocking layer129may be made of a material selected from among semiconductor materials having an empirical formula Inx1Aly1Ga1-x1-y1N (0≤x1≤1, 0≤y1≤1, and 0≤x1+y1≤1), for example, AlGaN, AlN, InAlGaN, and so on, but is not limited thereto.

According to an embodiment, the first conductive semiconductor layer124, the active layer126, the second conductive semiconductor layer127, and the blocking layer129may all contain aluminum. Accordingly, the first conductive semiconductor layer124, the active layer126, the second conductive semiconductor layer127, and the blocking layer129may have a composition of AlGaN, InAlGaN, or AlN.

The blocking layer129may have a higher aluminum composition than the well layer126a. For example, the aluminum composition of the blocking layer129may range from 50% to 100%. When the aluminum composition of the blocking layer129is greater than or equal to 50%, the blocking layer129may have an enough energy barrier to block first carriers and may be unable to absorb light emitted from the active layer126.

The blocking layer129may include a 1-1 section129aand a 1-2 section129c.

The 1-1 section129amay have an aluminum composition increasing from the first conductive semiconductor layer124toward the second conductive semiconductor layer127.

The aluminum composition of the 1-1 section129amay range from 80% to 100%. Accordingly, the 1-1 section129aof the blocking layer129may be a part having the highest aluminum composition in the semiconductor structure120.

The 1-1129amay include AlGaN or AlN. Alternatively, the 1-1 section129amay be a superlattice layer in which AlGaN and AlN are alternately disposed.

The 1-1 section129amay have a thickness ranging from about 0.1 nm to about 4 nm. In order to efficiently block the movement of first carriers to the second conductive semiconductor layer127, the 1-1 section129amay be formed to a thickness of 0.1 nm or greater. Also, in order to secure injection efficiency for second carriers injected from the second conductive semiconductor layer127to the active layer126, the 1-1 section129amay be formed to a thickness of 4 nm or less.

In an embodiment, the 1-1 section129ais formed to a thickness ranging from 0.1 nm to 4 nm in order to secure hole injection efficiency and electron blocking efficiency, but is not limited thereto. For example, when it is necessary to selectively further secure any one of the first-carrier blocking function and the second-carrier injection function, there may be a deviation from the aforementioned numerical range.

A 1-3 section129bdisposed between the 1-1 section129aand the 1-2 section129cmay include an undoped section, which contains no dopant. Accordingly, the 1-3 section129bmay serve to prevent the second dopant from spreading from the second conductive semiconductor layer127to the active layer126.

The second conductive semiconductor layer127may include a 2-1 conductive semiconductor layer127a, a 2-2 conductive semiconductor layer127b, and a 2-3 conductive semiconductor layer127c.

The 2-2 conductive semiconductor layer127bmay have a thickness greater than 10 nm and less than 50 nm. For example, the thickness of the 2-2 conductive semiconductor layer127bmay be equal to 25 nm. When the thickness of the 2-2 conductive semiconductor layer127bis greater than or equal to 10 nm, it is possible to secure electric current spreading characteristics of the 2-2 conductive semiconductor layer127b. Also, when the thickness is less than or equal to 50 nm, it is possible to secure injection efficiency for second carriers injected into the active layer126and reduce an absorption rate of light emitted from the active layer126in the 2-2 conductive semiconductor layer127b.

The 2-2 conductive semiconductor layer127bmay have a higher aluminum composition than the well layer126a. In order to generate ultraviolet light, the aluminum composition of the well layer126amay range from about 30% to about 70%. Accordingly, the aluminum composition of the 2-2 conductive semiconductor layer127bmay range from 40% to 80%.

It is possible to reduce absorption of light when the aluminum composition of the 2-2 conductive semiconductor layer127bis greater than or equal to 40% and also possible to reduce deterioration of electric current injection efficiency when the aluminum composition of the 2-2 conductive semiconductor layer127bis less than or equal to 80%. For example, when the aluminum composition of the well layer126ais equal to 30%, the aluminum composition of the 2-2 conductive semiconductor layer127bmay be equal to 40%.

The 2-1 conductive semiconductor layer127amay have a lower aluminum composition than the well layer126a. When the 2-1 conductive semiconductor layer127ahas a higher aluminum composition than the well layer126a, the 2-1 conductive semiconductor layer127ais unable to be sufficiently ohmic with a second electrode due to an increase in resistance therebetween, and also it is possible to reduce electric current injection efficiency.

The aluminum composition of the 2-1 conductive semiconductor layer127amay range from 1% to 50%. When the aluminum composition is less than or equal to 50%, it is possible to reduce resistance with the second electrode. When the aluminum composition is greater than or equal to 1%, it is possible to reduce absorption of light in the 2-1 conductive semiconductor layer127a. The 2-1 conductive semiconductor layer127amay have a lower aluminum composition than the intermediate layer124.

The 1-1 conductive semiconductor layer127amay have a thickness ranging from 1 nm to 30 nm. Accordingly, it may be advantageous, in terms of optical output power, that the 2-1 conductive semiconductor layer127abe adjusted to be as thin as possible because the 2-1 conductive semiconductor layer127ais able to absorb ultraviolet light.

However, when the thickness of the 2-1 conductive semiconductor layer127ais greater than or equal to 1 nm, it is possible to decrease resistance of the 2-1 conductive semiconductor layer127aand thus improve electrical characteristics of the semiconductor device. Also, when the thickness is less than or equal to 30 nm, it is possible to improve optical output power efficiency by decreasing the quantity of light absorbed by the 2-1 conductive semiconductor layer127a.

The 2-1 conductive semiconductor layer127amay have a smaller thickness than the 2-2 conductive semiconductor layer127b. A thickness ratio of the 2-1 conductive semiconductor layer127ato the 2-2 conductive semiconductor layer127bmay range from 1:1.5 to 1:20. When the thickness ratio is greater than 1:1.5, the thickness of the 2-2 conductive semiconductor layer127bincreases, and thus it is possible to improve electric current injection efficiency. Also, when the thickness ratio is less than 1:20, the thickness of the 2-1 conductive semiconductor layer127aincreases, and thus it is possible to reduce deterioration of crystallinity. When the 2-1 conductive semiconductor layer127ais too thin, it is necessary for the aluminum composition to be quickly changed in the range of the thickness, and thus it is possible to reduce the crystallinity.

The 2-2 conductive semiconductor layer127bmay have an aluminum composition decreasing away from the active layer126. Also, the 2-1 conductive semiconductor layer127amay have an aluminum composition decreasing away from the active layer126.

In this case, the 2-1 conductive semiconductor layer127amay have a greater reduction of aluminum with respect to thickness than the 2-2 conductive semiconductor layer127b. That is, the 2-1 conductive semiconductor layer127amay have a greater variation in aluminum composition in the direction of thickness than the 2-2 conductive semiconductor layer127b.

The 2-1 conductive semiconductor layer127amay have a lower aluminum composition than the well layer126ain order to achieve low contact resistance with the second electrode. Accordingly, the 2-1 conductive semiconductor layer127amay absorb a portion of the light emitted from the well layer126a.

Accordingly, in order to suppress absorption of light, the 2-1 conductive semiconductor layer127amay be formed to a thickness ranging from 1 nm to 30 nm.

As a result, the 2-1 conductive semiconductor layer127ahas a small thickness but a relatively high variation in aluminum. Thus, the 2-1 conductive semiconductor layer127amay have a relatively high reduction in aluminum with respect to thickness.

On the other hand, the 2-2 conductive semiconductor layer127bis thicker than the 2-1 conductive semiconductor layer127aand has a higher aluminum composition than the well layer126a. Thus, the 2-2 conductive semiconductor layer127bmay have a relatively slow reduction in aluminum.

Since the 2-1 conductive semiconductor layer127ais thin and has a large change in aluminum composition with respect to thickness, it is possible to change the aluminum composition while relatively slowly growing the 2-1 conductive semiconductor layer127a.

The 2-3 conductive semiconductor layer127cmay have a uniform aluminum composition. The 2-3 conductive semiconductor layer127cmay have a thickness ranging from 20 nm to 60 nm. The 2-3 conductive semiconductor layer127cmay have an aluminum composition ranging from 40% to 70%. When the aluminum composition of the 2-3 conductive semiconductor layer127cis greater than or equal to 40%, it is not possible to reduce crystallinity of the 2-1 conductive semiconductor layer127aand the 2-2 conductive semiconductor layer127b. When the aluminum composition is less than 70%, it is possible to prevent reduction of the crystallinity due to a rapid change in aluminum composition of the 2-1 conductive semiconductor layer127aand the 2-2 conductive semiconductor layer127b, thus enhancing electrical characteristics of the semiconductor device.

As described above, the 2-1 conductive semiconductor layer127amay have a thickness ranging from 1 nm to 10 nm, the 2-2 conductive semiconductor layer127bmay have a thickness ranging from 10 nm to 50 nm, and the 2-3 conductive semiconductor layer127cmay have a thickness ranging from 20 nm to 60 nm.

Accordingly, a ratio of the thickness of the 2-1 conductive semiconductor layer127ato the total thickness of the second conductive semiconductor layer127may range from 1:3 to 1:120. When the ratio is greater than 1:3, the 2-1 conductive semiconductor layer127amay secure the electrical characteristics (e.g., an operating voltage) of the semiconductor device. When the ratio is less than 1:120, the 2-1 conductive semiconductor layer127amay secure optical characteristics (e.g., optical output power) of the semiconductor device. However, the present invention is not limited thereto, and the ratio of the thickness of the 2-1 conductive semiconductor layer127ato the total thickness of the second conductive semiconductor layer127may range from 1:3 to 1:150 or range from 1:3 to 1:70.

The second conductive semiconductor layer127according to an embodiment of the present invention may have a first point P1with the highest aluminum composition in the semiconductor structure and a third point P3with the lowest aluminum composition in the semiconductor structure. Here, the first point P1may be the 1-1 section129aof the blocking layer129with the highest aluminum composition, and the third point P3may be the 2-1 conductive semiconductor layer127awith the smallest aluminum composition.

The first conductive semiconductor layer124may have a second point P2with the highest aluminum composition in the first conductive semiconductor layer and a fourth point P4with the lowest aluminum composition. The second point P2may be the 1-1 conductive semiconductor layer124aand/or the 1-2 conductive semiconductor layer124c, and the fourth point P4may be the intermediate layer124b.

The 1-1 section129amay have an aluminum composition ranging from 80% to 100%. The 2-1 conductive semiconductor layer127amay have an aluminum composition ranging from 1% to 50%. In this case, the 2-1 conductive semiconductor layer127amay have a lower aluminum composition than the well layer126a.

Accordingly, an aluminum composition ratio between the third point P3and the first point P1may range from 1:4 to 1:100. When the aluminum composition ratio is greater than or equal to 1:4, the aluminum composition of the first point P1may increase, thereby effectively blocking first carriers from passing through the second conductive semiconductor layer. When the aluminum composition ratio is less than or equal to 1:100, the aluminum composition of the third point P3may increase, thereby reducing absorption of light at the third point P3.

The 1-1 conductive semiconductor layer124amay have an aluminum composition ranging from 50% to 80%. The intermediate layer124bmay have an aluminum composition ranging from 30% to 70%. In this case, the intermediate layer124bmay have a lower aluminum composition than the 1-1 conductive semiconductor layer. Accordingly, an aluminum composition ratio between the fourth point P4and the second point P2may range from 1:0.5 to 1:0.9.

When the aluminum composition ratio is greater than or equal to 1:0.5, the aluminum composition of the 1-1 conductive semiconductor layer124amay increase, thereby enhancing the crystallinity. When the aluminum composition ratio is less than or equal to 1:0.9, the aluminum composition of the intermediate layer124bmay increase, thereby reducing absorption of ultraviolet wavelength light.

FIGS. 11A and 11Bshow SIMS data of a semiconductor structure according to an embodiment of the present invention,FIGS. 11C and 11Dshow SIMS data of a semiconductor structure according to another embodiment of the present invention,FIG. 12is a view showing an aluminum ion intensity ofFIGS. 11A to 11D,FIG. 13Ais a view showing SIMS data ofFIG. 12Athat is partially enlarged, andFIG. 13Bis a view showing SIMS data ofFIG. 12Bthat is converted to a linear scale.

Referring toFIG. 11A, the semiconductor structure may have compositions of aluminum (Al), gallium (Ga), a first dopant, a second dopant, oxygen (O), and carbon (C) changing in a direction from the first conductive semiconductor layer124to the second conductive semiconductor layer127. The first dopant may be silicon (Si), and the second dopant may be magnesium (Mg). However, the present invention is not limited thereto.

SIMS data may be analyzed through Time-of-Flight secondary ion mass spectrometry (TOF-SIMS).

SIMS data may be analyzed by emitting primary ions to a target surface and counting the number of secondary ions discharged. In this case, the primary ions may be selected from among 02+, Cs+, Bi+, and so on, an acceleration voltage may be adjusted in the range of about 20 keV to 30 keV, an emitted current may be adjusted in the range of about 0.1 pA to 5.0 pA, and a target area may be 20 nm×20 nm.

SIMS data may be obtained by collecting a secondary ion mass spectrum while gradually etching a surface (a point with a depth of zero) of the second conductive semiconductor layer in a direction toward the first conductive semiconductor layer.

However, the present invention is not limited thereto, and measurement conditions for detecting AlGaN-based and/or GaN-based semiconductor materials, first dopant materials, and second dopant materials may be variously used.

Also, a result of the SMIS analysis may be obtained by interpreting a spectrum for a secondary ion intensity or a doping concentration of each of the materials. When the secondary ion intensity or the doping concentration is interpreted, the result may include noise generated by a factor of 0.9 to 1.1. Accordingly, the term “the same/identical” refers to including noise scaled by a factor of 0.9 to 1.1 with respect to a specific secondary ion intensity or doping concentration.

The aluminum and gallium in the SIMS data ofFIGS. 11A to 11Dare spectrum data for the secondary ion intensity, and the first dopant, second dopant, oxygen, and carbon are data obtained by measuring the doping concentration. That is,FIGS. 11A to 11Dare placed in a single drawing to express SIMS data and doping concentration data.

Referring to11A, it is shown that a spectrum for an intensity level of aluminum and a spectrum for concentrations of the first and second dopants partially intersect each other. However, data regarding ion intensities and data regarding dopant concentrations may have an independent relation.

For example, it is shown that an aluminum ion intensity and a doping concentration of a second dopant intersect each other near the surface (the point having a depth of zero). However, when a doping concentration reference point (i.e., the lowest point in the left Y axis of this drawing) is set to be low, a doping concentration may decrease on the graph. For example, when a reference point of a second dopant doping concentration is decreased from 1.00E+14 to 1.00E+12, a second dopant concentration decreases on the graph, and thus second dopant data and aluminum data may not intersect each other.

A method of measuring concentrations of the first dopant, the second dopant, oxygen, or carbon is not limited to a specific form. Also, in this embodiment, a longitudinal axis (i.e., a Y axis) is shown and converted to a log scale.

It can be seen that an aluminum ion intensity gradually increases with depth from a surface and alternately increases and decreases after the maximum intensity point. Since a material AlGaN is formed by replacing an Al atom with a Ga atom in a GaN-based semiconductor material, a gallium ion intensity may be symmetrical to the aluminum ion intensity.

The ion intensity according to an embodiment may increase or decrease depending on measurement conditions. However, a secondary ion intensity (e.g., for an aluminum ion) may generally increases on the graph when a primary ion intensity increases and may generally decrease when the primary ion intensity decreases. Accordingly, the change in ion intensity in the direction of thickness may be similar even when measurement conditions are changed.

A doping concentration of a second dopant may be highest on a surface and may gradually decrease away from the surface. The second dopant may be present in all regions of the second conductive semiconductor layer and some regions of the active layer, but is not limited thereto. The second dopant may be placed in only the second conductive semiconductor layer, but may diffuse up to the active layer. Accordingly, it is possible to improve injection efficiency for the second dopant injected into the active layer. However, when the second dopant diffuses up to the first conductive semiconductor layer, a leakage current of the semiconductor device and/or non-radiative recombination between first and second carriers may occur, thereby reducing reliability and/or light emitting efficiency of the semiconductor device.

The first dopant may have a section R1between the first conductive semiconductor layer and the active layer in which the first dopant has a lower concentration than oxygen. The first dopant may be partially distributed even in the active layer. Accordingly, it is possible to improve injection efficiency for first carriers injected into the active layer and also possible to improve radiative recombination efficiency between first and second carriers.

It can be confirmed thatFIGS. 11B to 11Dshow the same tendency asFIG. 11A.

Referring toFIGS. 12 and 13A, an aluminum ion intensity may include aluminum ion intensities of first to sixth points P1, P2, P3, P4, P5, and P6.FIG. 12Ashows an aluminum ion intensity ofFIG. 11A,FIG. 12Bshows an aluminum ion intensity ofFIG. 11B,FIG. 12Cshows an aluminum ion intensity ofFIG. 11C, andFIG. 12Dshows an aluminum ion intensity ofFIG. 11D.

FIGS. 12C and 12Dshow distributions similar to a distribution for the aluminum ion intensity ofFIG. 12A, except for a concave-convex section P7between the first point P1and the third point P3in which the ion intensity changes. For example, according to embodiments ofFIGS. 12C and 12D, there is a structure in which a superlattice layer is additionally disposed on the blocking layer.

The aluminum ion intensity of the first point P1may be highest in the semiconductor structure120. Since the aluminum ion intensity of the first point P1is highest, it is possible to prevent first carriers from being non-radiatively recombined with second carriers in the second conductive semiconductor layer. Accordingly, it is possible to improve optical output power of the semiconductor device. The first point P1may be a region corresponding to the 1-1 section129aof the blocking layer129, but is not limited thereto.

A secondary ion intensity of the second point P2may correspond to a point having the highest aluminum ion intensity among points having aluminum ion intensities extending in a first direction D (i.e., a direction in which the depth increases) from the first point P1.

The second point P2may be a point of the first conductive semiconductor layer124having the highest aluminum ion intensity and also may be a point of the first conductive semiconductor layer124that is closest to the active layer126.

The second point P2may be used to balance concentrations or densities of first and second carriers that are recombined in the active layer by reducing first carrier energy injected into the active layer in the first conductive semiconductor layer124. Accordingly, it is possible to improve light emitting efficiency and thus optical output power characteristics of the semiconductor device.

A third ion intensity of the third point P3may correspond to a point having the lowest aluminum ion intensity in a direction from the first point P1to a surface of the semiconductor structure120(in a direction opposite to the first direction).

When the third point P3is in contact with the second electrode, resistance between the third point P3and the second electrode may be low because the aluminum ion intensity of the third point P3is lowest. Accordingly, it is possible to secure injection efficiency with which electric current is injected into the semiconductor structure120through the second electrode.

A fourth ion intensity of the fourth point P4may correspond to a point having the lowest aluminum ion intensity in the first direction from the second point P2.

When an LLO process is applied during a process for the semiconductor device, the fourth point P4may absorb laser light so that the laser light does not penetrate the active layer, thereby preventing damage to the active layer due to the LLO process.

Also, when the fourth point P4is in contact with the first electrode, it is possible to improve injection efficiency with which electric current is injected into the semiconductor structure by decreasing resistance between the first electrode and the fourth point P4. In this regard, the aluminum ion intensity of the fourth point P4may be lowest in the first direction from the second point P2.

The fifth point P5may be disposed between the second point P2and the fourth point P4. An aluminum ion intensity of the fifth point P5may be between those of the second point P2and the fourth point P4. The fifth point P5may be a single specific point or may be formed as a single layer. There may be an improvement in that a density per unit area of the electric current injected into the active layer is made to be uniform by the electric current injected through the fourth point P4being uniformly distributed in a layer including the fifth point P5.

Also, points (or layers) having the same or similar ion intensities of aluminum as or to the fifth point P5may be separately disposed in the first direction D from the fourth point P4. That is, there may be a section in which the ion intensity increases in the first direction from the fourth point P4. Accordingly, the fourth point P4may be disposed between the points (or layers) having the same aluminum ion intensity as the fifth point P5. However, the present invention is not limited thereto, and a region that is separated from the fifth point P5in the first direction D and spaced farther apart in the first direction D than the fourth point P4may have a higher aluminum ion intensity than the fifth point P5.

A tenth point P10may be disposed between the first point P1and the third point P3and may have the same aluminum ion intensity as a point S22having the smallest ion intensity between the first point P1and the second point P2.

A region between the tenth point P10and the third point P3may have a thickness ranging from 1 nm to 30 nm in order to suppress absorption of light emitted by the semiconductor device and decrease contact resistance with the second electrode.

Also, the third point P3electrically connected with the second electrode may have a lower electrical conductivity than the fourth point P4connected with the first electrode. Accordingly, the third point P3may have a smaller ion intensity than the fourth point P4.

An average variation in aluminum ion intensity between the tenth point P10and the third point P3may be greater than an average variation in aluminum ion intensity between the first point P1and the tenth point P10. Here, the average variation may be obtained by dividing the maximum variation in aluminum ion intensity by thickness.

A region S11between the third point P3and the tenth point P10may have a section in which the aluminum ion intensity decreases toward a surface S0and a reverse section P6in which the aluminum ion intensity does not decrease toward the surface S0. The reverse section P6may be a section in which the aluminum ion intensity increases toward the surface S0or is maintained.

When the reverse section P6is disposed in the region between the third point P3and the tenth point P10, electric current injected through the third point P3may be uniformly spread, and thus density of electric current injected into the active layer may be controlled to be uniform. Accordingly, it is possible to enhance optical output power characteristics and electrical characteristics of the semiconductor device.

The reverse section P6may be controlled through temperature. For example, the region between the third point P3and the tenth point P10may have an aluminum composition controlled through temperature control. In this case, when the temperature is too rapidly lowered, it is possible to significantly reduce crystallinity of the second conductive semiconductor layer.

Accordingly, during a process for continuously lowering or raising temperature, a large amount of aluminum is instantly contained at the moment when a temperature having been lowered is raised, and thus it is possible to create the reverse section P6.

That is, during a process of forming the third point P3after the tenth point P10having the same aluminum ion intensity as a point having the smallest aluminum ion intensity in the active layer is formed, it is possible to control an aluminum composition through temperature and to place the reverse section P6in order to secure crystallinity of the second conductive semiconductor layer and secure electric current spreading characteristics.

However, the present invention is not limited thereto. According to another embodiment, in order to further secure the electric current injection characteristics, the aluminum ion intensity may continuously decrease in a direction from the tenth point P10to the third point P3without the reverse section P6.

Referring toFIG. 13A, in a graph for aluminum ion intensity, the semiconductor structure may include a first section S1, a second section S2, and a third section S3in a direction in which the depth increases.

The first section S1may be disposed between the first point P1and the third point P3and may be configured as the second conductive semiconductor layer127. The second section S2may be disposed between the first point P1and the second point P2and may be configured as the active layer126. The third section S3may be disposed in the first direction from the second point P2and may be configured as the first conductive semiconductor layer124.

The second section S2may be disposed between the first point P1and the second point P2. As described above, the first point P1may be a point having the highest aluminum intensity of aluminum in the semiconductor structure, and the second point P2may be a point that is separately disposed in the first direction away from the surface on this drawing (in a direction in which the depth increases) and has an ion intensity higher than the maximum ion intensity (a peak ion intensity) of the second section S2.

However, the present invention is not limited thereto, and the second point may have the same height as the fifth point. In this case, the second section may be disposed between the first point and the fifth point.

The second section S2is a section corresponding to the active layer126and may have a plurality of peaks S21and a plurality of valleys S22. A valley S22may be an ion intensity of the well layer, and a peak S21may be an ion intensity of the barrier layer.

An ion intensity ratio M1of a point of the valley S22having the lowest ion intensity to the first point P1may range from 1:0.4 to 1:0.6, and an ion intensity ratio M2of the valley S22to the peak S21may range from 1:0.5 to 1:0.75.

When the aluminum ion intensity ratio M1of the point of the valley S22having the lowest ion intensity to the first point P1is greater than or equal to 1:0.4, it is possible to secure crystallinity of the second conductive semiconductor layer between the first point P1and the third point P3that are disposed closer than the active layer and also to prevent injection of first carriers into the second conductive semiconductor layer to increase the probability of radiative recombination in the active layer. Accordingly, it is possible to improve optical output power characteristics of the semiconductor device.

Also, when the ion intensity ratio M1is less than or equal to 1:0.6, it is possible to secure crystallinity of the second conductive semiconductor layer between the first point P1and the third point P3that are disposed closer to the surface than the active layer.

When the ion intensity ratio M2of the valley S22to the peak S21is greater than or equal to 1:0.5, it is possible for the barrier layer to effectively prevent carriers from flowing out from the well layer included in the active layer to the first conductive semiconductor layer and/or the second conductive semiconductor layer to increase the probability of radiative recombination in the well layer, thus enhancing optical output power characteristics of the semiconductor device.

Also, when the ion intensity ratio M2is less than or equal to 1:0.75, it is possible to secure crystallinity of the semiconductor structure, reduce a change in wavelength due to strain, and/or increase the probability of radiative recombination by reducing stress due to a difference in lattice constant between the well layer and the barrier layer.

A ratio of the ratio M1to the ratio M2may satisfy a range of 1:0.3 to 1:0.8. Accordingly, a section in which the ratio of the ratio M1to the ratio M2satisfies a range of 1:0.3 to 1:0.8 may be a section in which the active layer is actually disposed.

The ion intensity of the third point P3may have an ionic intensity less than the smallest ion intensity in the second section S2(i.e., the ion intensity of the well layer). In this case, the active layer may be included in the second section S2and may be defined as a region between a valley P8closest to the first point P1and a valley P9farthest from the first point P1.

Also, a distance between adjacent valleys S22may be smaller than a distance between the first point P1and the second point P2. This is because the thickness of the well layer and the barrier layer is smaller than the entire thickness of the active layer126.

The first section Si may include a surface region S11having a smaller ion intensity than the fourth point P4. In this case, the ion intensity of the surface region S11may decrease in the direction opposite to the first direction D.

According to the SIMS data, a ratio of a first intensity difference D1between the second point P2and the fourth point P4to a second intensity difference D2between the first point P1and the third point P3(D1:D2) may range from 1:1.5 to 1:2.5. When the intensity difference ratio D1:D2is greater than or equal to 1:1.5 (e.g., 1:1.6), the second intensity difference D2decreases and thus it is possible to sufficiently reduce the aluminum composition of the first point P1. Accordingly, it is possible to reduce contact resistance with the second electrode.

Also, when the intensity difference ratio D1:D2is less than or equal to 1:2.5 (e.g., 1:2.4), it is possible to prevent light emitted by the active layer126from being absorbed by the 2-1 conductive semiconductor layer127adue to a too low aluminum composition and thus prevent a degradation of the optical characteristics of the semiconductor.

A ratio of a third intensity difference D3between the seventh point P7and the first point P1to a fourth intensity difference D4between the fourth point P4and the third point P3(D3:D4) may range from 1:0.2 to 1:2 or range from 1:0.2 to 1:1.

When the intensity difference ratio is greater than or equal to 1:0.2, the fourth intensity difference D4relatively increases, and thus it is possible to sufficiently reduce the aluminum composition. Accordingly, it is possible to reduce contact resistance with the second electrode. Also, when the composition ratio is less than or equal to 1:2, it is possible to prevent a reduction in crystallinity due to a rapid change in aluminum composition in a range of thickness of the 2-1 conductive semiconductor layer127a. Also, it is possible to prevent light emitted by the active layer126from being absorbed by the 2-1 conductive semiconductor layer127adue to a too low aluminum composition.

Conventionally, a thin GaN layer was inserted for ohmic contact between the second conductive semiconductor layer127and the electrode. However, in this case, since the GaN layer in contact with the electrode does not contain aluminum, the aluminum ion intensity of the third point P3is not measured or is significantly reduced. Accordingly, the ratio of the first intensity difference D1to the second intensity difference D2(D1:D2) and the ratio of the third intensity difference D3to the fourth intensity difference D4(D3:D4) may depart from the aforementioned range.

A ratio of the intensity difference between the first point P1and the third point P3to the intensity difference between the fifth point P5and the third point P3may range from 1:0.5 to 1:0.8. When the intensity difference ratio is greater than or equal to 1:0.5, the intensity of the fifth point P5increases. Thus, it is possible to enhance the crystallinity and increase the light extraction efficiency. Also, when the intensity difference ratio is less than 1:0.8, it is possible to mitigate a lattice mismatch between the active layer126and the first conductive semiconductor layer124.

An ion intensity ratio of the third point P3to the first point P1(P3:P1) may range from 1:2 to 1:4. When the ion intensity ratio of the third point P3to the first point P1is greater than or equal to 1:2 (e.g., 1:2.1), the intensity of third point P3is sufficiently reduced, and thus it is possible to reduce contact resistance with the second electrode. Also, when the ion intensity ratio of the third point P3to the first point P1is less than or equal to 1:4 (e.g., 1:3.9), the aluminum intensity of the third point P3may increase. Accordingly, it is possible to prevent light from being absorbed at the third point P3.

An ion intensity ratio of the tenth point P10to the first point P1may range from 1:1.3 to 1:2.5. When the ion intensity ratio of the tenth point P10to the first point P1is greater than or equal to 1:1.3, the ion intensity of the first point P1increases, and thus it is possible to effectively prevent first carriers from passing through the active layer. When the ion intensity ratio of the tenth point P10to the first point P1is less than or equal to 1:2.5, the ion intensity of the tenth point P10increases, and thus it is possible for the well layer to generate ultraviolet wavelength light.

An ion intensity ratio of the third point P3to the fourth point P4may range from 1:1.1 to 1:2. When the ion intensity ratio of the third point P3to the fourth point P4is greater than or equal to 1:1.1, the ion intensity of the fourth point P4increases, and thus it is possible to reduce the absorption rate of ultraviolet wavelength light. Also, when the ion intensity ratio of the third point P3to the fourth point P4is less than or equal to 1:2, the ion intensity of the third point is sufficiently secured, and thus it is possible to reduce the absorption rate of ultraviolet wavelength light.

An ion intensity ratio of the second point P2to the first point P1may range from 1:1.1 to 1:2. When the ion intensity ratio of the second point P2to the first point P1is greater than or equal to 1:1.1, the ion intensity of the first point P1increases, and thus it is possible to effectively prevent first carriers from passing through the active layer. Also, when the ion intensity ratio of the second point P2to the first point P1is less than or equal to 1:2, first carriers and second carriers that are injected into the active layer and radiatively recombined with each other may be balance in concentration, and it is possible to enhance the quantity of light emitted by the semiconductor device.

An ion intensity ratio of the fourth point P4to the second point P2may range from 1:1.2 to 1:2.5. When the ion intensity ratio of the fourth point P4to the second point P2is greater than or equal to 1:1.2, it is possible to reduce resistance between the fourth point P4and the first electrode. Also, when the ion intensity ratio of the fourth point P4to the second point P2is less than or equal to 1:2.5, the ion intensity of the fourth point P4increases, and thus it is possible to reduce the absorption rate of ultraviolet wavelength light.

An ion intensity ratio of the fifth point P5to the second point P2may range from 1:1.1 to 1:2.0. According to an embodiment, a semiconductor structure for emitting deep-ultraviolet light may be made of a GaN-based material containing a large amount of aluminum, compared to a semiconductor structure for emitting blue light. Accordingly, the semiconductor structure for emitting deep-ultraviolet light may have a different ratio of a mobility of first carriers to a mobility of second carriers from the semiconductor structure for emitting blue light. That is, when the ion intensity ratio of the fifth point P5to the second point P2is greater than or equal to 1:1.1, it is possible to secure the concentration of first carriers injected into the active layer. Also, when the ion intensity ratio of the fifth point P5to the second point P2is less than or equal to 1:2.0, the ion intensity of the fifth point P5increases, and thus it is possible to improve the crystallinity.

An ion intensity ratio of the fourth point P4to the fifth point P5may range from 1:1.1 to 1:2.0. When the ion intensity ratio of the fourth point P4to the fifth point P5is greater than or equal to 1:1.1, the ion intensity of the fifth point P5increases, and thus it is possible to improve the crystallinity. Also, when the ion intensity ratio of the fourth point P4to the fifth point P5is less than or equal to 1:2.0, the ion intensity of the fourth point P4increases, and thus it is possible to reduce the absorption rate of ultraviolet wavelength light.

InFIGS. 12 and 13A, the aluminum ion intensities are represented in log scale. However, the present invention is not limited thereto, and the aluminum ion intensities are represented in linear scale.

According to an embodiment, it can be seen that the first point P1and the third point P3are actually placed within a single order because the third point P3contains aluminum. The order may be a level unit of the ion intensity. For example, a first order may be 1.0×101, and a second order may be 1.0×102. Also, each order may have ten sub-levels.

For example, a first sub-level of the first order may be 1.0×101, a second sub-level of the first order may be 2.0×101, a third sub-level of the first order may be 3.0×101, a ninth sub-level of the first order may be 9.0×101, and a tenth sub-level of the first order may be 1.0×102. That is, the tenth sub-level of the first order may be equal to the first sub-level of the second order. InFIG. 13B, dotted lines are expressed for each two sub-levels.

FIG. 14Ais a conceptual diagram of a second conductive semiconductor layer according to an embodiment of the present invention,FIG. 14Bshows AFM data obtained by measuring the surface of the second conductive semiconductor layer according to an embodiment of the present invention,FIG. 14Cshows AFM data obtained by measuring a surface of a GaN thin film, andFIG. 14Dshows AFM data obtained by measuring a surface of the second conductive semiconductor layer grown at high speed.

Referring toFIG. 14A, a second conductive semiconductor layer127according to an embodiment may include a 2-1 conductive semiconductor layer127a, a 2-2 conductive semiconductor layer127b, and a 2-3 conductive semiconductor layer127c. The 2-1 conductive semiconductor layer127amay be a contact layer that is in contact with a second electrode. As features of the layers, the above description may be applied as it is.

A surface of the 2-1 conductive semiconductor layer127amay include a plurality of clusters C1. Each of the clusters C1may be a protrusion protruding from the surface. For example, each of the clusters C1may be a protrusion protruding more than about 10 or 20 nm from the average surface height. Each of the clusters C1may be formed due to a lattice mismatch between aluminum (Al) and gallium (Ga).

According to an embodiment, the 2-1 conductive semiconductor layer127acontains aluminum, has a large variation in aluminum with respect to thickness, and is thinner than other layers. Thus, the 2-1 conductive semiconductor layer127ais formed on the surface not in the form of a single layer but in the form of clusters C1. Each of the clusters C1may contain Al, Ga, N, Mg, or the like. However, the present invention is not limited thereto.

Referring toFIG. 14B, it can be seen that clusters C1is formed on the surface of the second conductive semiconductor layer127in the shape of relatively bright dots. According to an embodiment, the 2-1 conductive semiconductor layer127ahas an aluminum composition ranging from 1% to 10%, and thus the 2-1 conductive semiconductor layer127amay be formed in the form of clusters C1to increase a bonding area. Accordingly, it is possible to enhance electrical characteristics.

One to eight clusters C1may be observed per average 1 μm2 on the surface of the second conductive semiconductor layer127. Here, the average value is the average of values measured at about 10 or more different positions. A result obtained by measuring a position E1ofFIG. 14Bwas that 12 clusters C1were observed per unit area, which is 2 μm×2 μm. Only clusters C1protruding more than 25 nm from the surface were measured. By adjusting contrast in an AFM image, it is possible to ensure that only clusters protruding more than 25 nm from the surface may be output.

The clusters C1, using converted units based on the measurement result, may have a density ranging from 1×10-8/cm2 to 8×10-6/cm2. When the density of the clusters C1is less than 1×10-8/cm2, a contact area relatively decreases, and thus it is possible to increase contact resistance with the second electrode.

Also, when the density of the clusters C1is greater than 8×10-6/cm2, light emitted by the active layer126is absorbed by Ga contained in some of the clusters, and thus it is possible to reduce optical output power.

According to an embodiment, the density of the clusters C1may satisfy 1×10-8/cm2 to 8×10-6/cm2. Accordingly, it is possible to reduce the contact resistance with the second electrode while not reducing the optical output power.

Referring toFIG. 14C, it can be seen that no cluster was observed from the surface of the GaN thin film. This is because the GaN thin film is formed as a single layer as the density of the clusters increases. Accordingly, it can be seen that no cluster is formed on the contact surface when the GaN thin film is formed between the second conductive semiconductor layer and the second electrode.

Referring toFIG. 14D, it can be seen that clusters are not grown well when the second conductive semiconductor layer is grown at high speed. Accordingly, it can be seen that no clusters C1are formed when the second conductive semiconductor layer is grown at high speed although the aluminum composition of the second conductive semiconductor layer is controlled to range from 1% to 10% in the surface thereof. For example,FIG. 14Dis a photograph obtained by measuring the surface after P-AlGaN is grown at a speed of 0.06 nm/s.

That is, it can be seen that a surface layer should have an aluminum composition ranging from 1% to 10% and also a sufficiently low growth speed in order to form a plurality of clusters C1in the second conductive semiconductor layer127.

According to an embodiment, the 2-1 conductive semiconductor layer may have a lower growth speed than the 2-2 conductive semiconductor layer and the 2-3 conductive semiconductor layer. For example, a growth speed ratio of the 2-2 conductive semiconductor layer to the 2-1 conductive semiconductor layer may range from 1:0.2 to 1:0.8. When the growth speed ratio is less than 1:0.2, the growth speed of the 2-1 conductive semiconductor layer is so low that AlGaN having a high aluminum composition may be grown by etching Ga at a high temperature at which AlGaN is grown, and thus it is possible to degrade ohmic characteristics thereof. When the growth speed ratio is greater than 1:0.8, the growth speed of the 2-1 conductive semiconductor layer is so high that it is possible to reduce the crystallinity.

FIG. 15is a conceptual view of a semiconductor device according to an embodiment of the present invention,FIGS. 16A and 16Bare views illustrating a configuration in which optical output power is enhanced depending on a change in number of recesses, andFIG. 17is an enlarged view of a part A ofFIG. 15.

Referring toFIG. 15, a semiconductor device according to an embodiment may include a semiconductor structure120including a first conductive semiconductor layer124, a second conductive semiconductor layer127, and an active layer126, a first electrode142electrically connected with the first conductive semiconductor layer124, and a second electrode146electrically connected with the second conductive semiconductor layer127.

The first conductive semiconductor layer124, the active layer126, and the second conducive semiconductor layer127may be disposed in a first direction (i.e., a Y direction). Here, the first direction (i.e., the Y direction), which is a thickness direction of each layer, is defined as a vertical direction, and a second direction (i.e., the X direction) perpendicular to the first direction (i.e., the Y direction) is defined as a horizontal direction.

All of the above-described structures may be applied to the semiconductor structure120according to an embodiment. The semiconductor structure120may include a plurality of recesses128disposed even in a portion of the first conductive semiconductor layer124through the second conductive semiconductor layer127and the active layer126.

The first electrode142may be disposed on top of the recesses128and electrically connected with the first conductive semiconductor layer124. The second electrode146may be formed under the second conductive semiconductor layer127.

Each of the first electrode142and the second electrode146may be an ohmic electrode. Each of the first electrode142and the second electrode146may be made of at least one of indium tin oxide (ITO), indium zinc oxide (IZO), indium zinc tin oxide (IZTO), indium aluminum zinc oxide (IAZO), indium gallium zinc oxide (IGZO), indium gallium tin oxide (IGTO), aluminum zinc oxide (AZO), antimony tin oxide (ATO), gallium zinc oxide (GZO), IZO nitride (IZON), Al—Ga ZnO (AGZO), In—Ga ZnO (IGZO), ZnO, IrOx, RuOx, NiO, RuOx/ITO, Ni/IrOx/Au, Ni/IrOx/Au/ITO, Ag, Ni, Cr, Ti, Al, Rh, Pd, Ir, Sn, In, Ru, Mg, Zn, Pt, Au, and Hf, but is not limited thereto. For example, the first electrode may have a plurality of metal layers (e.g., Cr, Al, and Ni), and the second electrode may be made of ITO.

Referring toFIG. 16A, when a GaN-based semiconductor structure120emits ultraviolet light, the GaN-based semiconductor structure120may contain aluminum. When the aluminum composition of the semiconductor structure120increases, it is possible to reduce electric current spreading characteristics in the semiconductor structure120. Also, when the active layer126contains aluminum and emits ultraviolet light, the active layer126may have an increasing quantity of light emitted to the side, compared to a GaN-based blue light emitting device (TM mode). The TM mode may mainly occur in an ultraviolet semiconductor device.

The ultraviolet semiconductor device has reduced electric current spreading characteristics, compared to a blue GaN-based semiconductor device. Accordingly, the ultraviolet semiconductor device needs to have a relative large number of first electrodes142disposed therein, compared to the blue GaN-based semiconductor device.

When the aluminum composition increases, the electric current spreading characteristics may deteriorate. Referring toFIG. 16A, electric current is spread at only points adjacent to each of the first electrodes142, and an electric current density may rapidly decrease at points far from each of the first electrodes142. Accordingly, it is possible for an effective light emitting region P2to become narrow.

A region up to a boundary having an electric current density of 40% or less with respect to the first electrode142having the highest electric current density may be defined as the effective light emitting region P2. For example, the effective light emitting region P2may be adjusted in a range less than 40 μm from the center of each of the recesses128depending on the injected electric current level and the aluminum composition.

A low electric current density region P3may have a lower electric current density and thus a smaller quantity of light than the effective light emitting region P2. Accordingly, it is possible to enhance the optical output power by placing a larger number of first electrodes142in the low electric current density region P3, which has a low electric current density, or by using a reflective structure.

Generally, since a GaN semiconductor layer that emits blue light has relatively good electric current spreading characteristics, it is preferable that the areas of the recesses128and the first electrode142be minimized. This is because the area of the active layer126decreases as the areas of the recesses128and the first electrode142increase. However, according to an embodiment, the electric current spreading characteristics are relatively low because the aluminum composition is high. Accordingly, it may be preferable to reduce the low electric current density region P3by increasing the area and/or number of first electrodes142although reducing the area of the active layer126or to place a reflective structure in the low electric current density region P3.

Referring toFIG. 6B, when the number of recesses128increases to 48, the recesses128may be arranged in a zigzag form instead of being straightly arranged in a horizontal or vertical direction. In this case, the area of the low electric current density region C3may be decreased, and thus most of the active layer126may participate in light emission.

An ultraviolet light emitting device may have reduced electric current spreading characteristics in the semiconductor structure120. Thus, smooth injection of electric current is needed to secure uniform electric current density characteristics in the semiconductor structure120and secure electrical and optical characteristics and reliability of the semiconductor device. Accordingly, in order to smoothly inject electric current, a relatively large number of recesses128may be formed, compared to the GaN-based semiconductor structure120, and then the first electrode142may be disposed on the recesses128.

Referring toFIG. 17, a first insulation layer131may electrically insulate the first electrode142from the active layer126and the second conductive semiconductor layer127. Also, the first insulation layer131may electrically insulate the second electrode146and a second conductive layer150from a first conductive layer165. Also, the first insulation layer131may function to prevent oxidation of the side of the active layer126during the process for the semiconductor device.

The first insulation layer131may be made of at least one material selected from a group consisting of SiO2, SixOy, Si3N4, SixNy, SiOxNy, Al2O3, TiO2, and AlN, but is not limited thereto. The first insulation layer131may be formed in single or multiple layers. For example, the first insulation layer131may be a distributed Bragg reflector (DBR) having a multi-layered structure including a Si oxide or a Ti compound. However, the present invention is not limited thereto, and the first insulation layer131may include various reflective structures.

When the first insulation layer131has a reflective function, the first insulation layer131may upwardly reflect light emitted horizontally from the active layer126, thereby enhancing light extraction efficiency. In this case, the light extraction efficiency may increase as the number of recesses128increases.

The first electrode142may have a diameter W3ranging from 24 μm to 50 μm. When this range is satisfied, this is advantageous in spreading electric current, and it is possible to place a large number of first electrodes142. When the diameter W3of the first electrode142is greater than or equal to 24 μm, it is possible to sufficiently secure electric current injected into the first conductive semiconductor layer124. When the diameter W3of the first electrode142is less than or equal to 50 μm, it is possible to sufficiently secure the number of first electrodes142placed in the area of the first conductive semiconductor layer124and also secure electric current spreading characteristics.

Each of the recesses128may have a diameter W1ranging from 38 μm to 60 μm. The diameter W1of each of the recesses128may be defined to be the greatest area of a recess disposed under the second conductive semiconductor layer127. The diameter W1of each of the recesses128may be a diameter of a recess disposed at a bottom surface of the second conductive semiconductor layer127.

When the diameter W1of each of the recesses128is greater than or equal to 38 μm, it is possible to secure a process margin for an area in which the first electrode142is electrically connected with the first conductive semiconductor layer124while the first electrode142to be disposed inside each of the recesses128is formed. When the diameter W1of each of the recesses128is less than or equal to 60 μm, it is possible to prevent reduction in the volume of the active layer126in order to place the first electrode142, and thus light emitting efficiency may deteriorate.

Each of the recesses128may have a slope angle θ5ranging from 70 degrees to 90 degrees. When this range is satisfied, this is advantageous in forming the first electrode142on top of the recesses128, and it is possible to form a large number of recesses128.

When the slope angle θ5is less than 70 degrees, a removed area of the active layer126may increase, but an area where the first electrode142is to be placed may decrease. Accordingly, it is possible to reduce electric current injection characteristics and also light emitting efficiency. Accordingly, it is possible to adjust an area ratio of the first electrode142to the second electrode146by using the slope angle θ5of each of the recesses128.

The second electrode146may be thinner than the first insulation layer131. Accordingly, it is possible to secure step coverage characteristics of the second conductive layer150and a second insulation layer132that surround the second electrode146and to improve reliability of the semiconductor device. The second electrode146may be disposed a first separation distance Si of about 1 μm to 4 μm apart from the first insulation layer131. When the separation distance is greater than or equal to 1 μm, it is possible to secure a process margin for placing the second electrode146with respect to the first insulation layer131, thus improving electrical characteristics, optical characteristics, and reliability of the semiconductor device. When the separation distance is less than or equal to 4 μm, it is possible to secure the entire area where the second electrode146may be placed and to improve operating voltage characteristics of the semiconductor device.

The second conductive layer150may cover the second electrode146. Accordingly, a second electrode pad166, the second conductive layer150, and the second electrode146may form one electrical channel.

The second conductive layer150may fully surround the second electrode146and may be in contact with one side surface and an upper surface of the first insulation layer131. The second conductive layer150may be made of a material having good adhesion to the first insulation layer131and made of at least one material selected from a group consisting of Cr, Al, Ti, Ni, and Au or an alloy thereof. Also, the second conductive layer150may be formed in single or multiple layers.

When the second conductive layer150is in contact with the side surface and the bottom surface of the first insulation layer131, it is possible to enhance thermal and electrical reliability of the second electrode146. The second conductive layer150may extend to a lower portion of the first insulation layer131. In this case, it is possible to suppress detachment of an end portion of the first insulation layer131. Accordingly, it is possible to prevent penetration of external moisture or contaminants Also, the second conductive layer150may have a reflective function for upwardly reflecting light emitted from a gap between the first insulation layer131and the second electrode146.

The second conductive layer150may be disposed a first separation distance S1between the first insulation layer131and the second electrode146. That is, the second conductive layer150may be disposed a first separation distance S1in contact with one side surface and an upper surface of the second electrode146and one side surface and an upper surface of the first insulation layer131. Also, a region where a Schottky junction is formed by the second conductive semiconductor layer126coming into contact with the second conductive layer150may be placed within the first separation distance S1. By forming the Schottky junction, it is possible to facilitate distribution of electric current. However, the present invention is not limited thereto, and the placement may be freely performed as long as resistance between the second electrode146and the second conductive semiconductor layer127is greater than the resistance between the second conductive layer150and the second conductive semiconductor layer127.

The second insulation layer132may electrically insulate the second electrode146and the second conductive layer150from the first conductive layer165. The first conductive layer165may be electrically connected to the first electrode142via the second insulation layer132. The second insulation layer132and the first insulation layer131may be made of the same material or different materials.

According to an embodiment, the second insulation layer132is disposed between the first electrode142and the second electrode146and over the first insulation layer131, and thus it is possible to prevent penetration of external moisture and/or other contaminants even when a defect occurs in the first insulation layer131.

For example, when the first insulation layer131and the second insulation layer132is formed as a single layer, a defect such as a crack may easily propagate in a thickness direction. Accordingly, external moisture or contaminants may penetrate into the semiconductor structure through the exposed defect.

However, according to an embodiment, the second insulation layer132is separately disposed over the first insulation layer131, and thus it is difficult for a defect formed in the first insulation layer131to propagate to the second insulation layer132. That is, an interface between the first insulation layer131and the second insulation layer132serves to block propagation of the defect.

Referring toFIG. 15again, the second conductive layer150may electrically connect the second electrode with the second electrode pad166.

The second electrode146may be directly disposed on the second conductive semiconductor layer127. When the second conductive semiconductor layer127is made of AlGaN, holes may not be smoothly injected because of a lower electrical conductivity. Accordingly, there is a need to appropriately adjust an aluminum composition of the second conductive semiconductor layer127. This will be described later.

The second conductive layer150may be made of at least one material selected from a group consisting of Cr, Al, Ti, Ni, and Au or an alloy thereof. Also, the second conductive layer150may be formed in single or multiple layers.

The first conductive layer165and a bonding layer160may be disposed according to the bottom surface of the semiconductor structure120and the shape of the recesses128. The first conductive layer165may be made of a good reflective material. For example, the first conductive layer165may contain aluminum. When the first conductive layer165contains aluminum, the first conductive layer165may serve to upwardly reflect light that is emitted by the active layer126in a direction toward a substrate, thereby enhancing light extraction efficiency. However, the present invention is not limited thereto, and the first conductive layer165may provide a function for electrically connecting to the first electrode142. The first conductive layer165may not contain a high reflective material, for example, aluminum and/or silver (Ag). In this case, a reflective metal layer (not shown) containing a high reflective material may be disposed between the first conductive layer165and the first electrode142disposed in the recess128and between the second conductive semiconductor layer127and the first conductive layer165.

The bonding layer160may contain a conductive material. For example, the bonding layer160may contain a material selected from a group consisting of gold, tin, indium, aluminum, silicon, silver, nickel, and copper or an alloy thereof.

The substrate170may be made of a conductive material. For example, the substrate170may contain a metal or a semiconductor material. For example, the substrate170may be made of a metal having good electrical conductivity and/or thermal conductivity. In this case, heat generated while the semiconductor device operates may be quickly released to the outside. Also, when the substrate170is made of a conductive material, the first electrode142may receive electric current supplied from an external source through the substrate170.

The substrate170may contain a material selected from a group consisting of silicon, molybdenum, tungsten, copper, and aluminum or an alloy thereof.

A passivation layer180may be disposed on an upper surface and one side surface of the semiconductor structure120. The passivation layer180may have a thickness ranging from 200 nm to 500 nm. When the thickness is greater than or equal to 200 nm, the device may be protected from external moisture or foreign materials, and thus it is possible to improve electrical and optical reliability. When the thickness is less than or equal to 500 nm, it is possible to reduce stress applied to the semiconductor device and also to prevent an increase in cost of the semiconductor due to a reduction in optical and electrical reliability of the semiconductor device or an extension of a processing time for the semiconductor device.

A square wave pattern may be formed on an upper surface of the semiconductor structure120. The square wave pattern may enhance extraction efficiency of light emitted from the semiconductor structure120. The square wave pattern may have a different average height depending on ultraviolet wavelengths, and UV-C light has an average height ranging from 300 nm to 800 nm. When the average height ranges from 500 nm to 600 nm, it is possible to enhance light extraction efficiency.

FIG. 18is a conceptual view of a semiconductor device according to another embodiment of the present invention, andFIG. 19is a plan view ofFIG. 18.

Referring toFIG. 18, the above-described configuration may be applied to a semiconductor structure120as it is. Also, a plurality of recesses128may be disposed even in a portion of a first conductive semiconductor layer124through a second conductive semiconductor layer127and an active layer126.

The semiconductor device may include a side reflector Z1disposed on an edge thereof. The side reflector Z1may be formed by a second conductive layer150, a first conductive layer165, and a substrate170protruding in a thickness direction (a Y axis direction). Referring toFIG. 20, the side reflector Z1may be disposed along the edge of the semiconductor device to surround the semiconductor structure120.

The second conductive layer150of the side reflector Z1protrudes further than the active layer126so that the second conductive layer150may upwardly reflect light emitted by the active layer126. Accordingly, without a separate reflective layer being formed, it is possible to upwardly reflect light emitted in a horizontal direction (an X axis direction) at an outermost portion thereof because of the TM mode.

The side reflector Z1may have a slope angle greater than 90 degrees and less than 145 degrees. The slope angle may be an angle of the second conductive layer150with respect to a horizontal plane (i.e., an XZ plane). When the angle is less than 90 degrees or greater than 145 degrees, it is possible for there to be a reduction in efficiency with which light traveling toward the side is reflected upward.

FIG. 20is a conceptual view of a semiconductor device package according to an embodiment of the present invention,FIG. 21is a plan view of a semiconductor device package according to an embodiment of the present invention,FIG. 22is a modification ofFIG. 21, andFIG. 23is a sectional view of a semiconductor device package according to another embodiment of the present invention.

Referring toFIG. 20, the semiconductor device package may include a body2having a groove (i.e., an opening)3, a semiconductor device1disposed in the body2, and a pair of lead frames5aand5bdisposed in the body2and electrically connected to the semiconductor device1. The semiconductor device1may include all of the above-described elements.

The body2may include an ultraviolet light reflective material or a coating layer. The body2may be formed by stacking a plurality of layers2a,2b,2c,2d, and2e. The plurality of layers2a,2b,2c,2d, and2emay be made of the same material or contain different materials. For example, the plurality of layers2a,2b,2c,2d, and2emay contain aluminum.

The groove3may have a width increasing away from the semiconductor device and an inclined surface having a stepped portion3aformed therein.

A light transmitting layer4may cover the groove3. The light transmitting layer4may be made of glass, but is not limited thereto. There is no limitation in material of the light transmitting layer4as long as the material can effectively transmit ultraviolet light. The groove3may have an empty space formed therein.

Referring toFIG. 21, a semiconductor device10may be disposed on a first lead frame5aand connected with a second lead frame5bby wires. In this case, the second lead frame5bmay be disposed to surround side surfaces of the first lead frame5a.

Referring toFIG. 22, the semiconductor device package may have a plurality of semiconductor devices10a,10b,10c, and10ddisposed therein. In this case, the lead frame may include a first lead frame5a, a second lead frame5b, a third lead frame5c, a fourth lead frame5d, and a fifth lead frame5e.

The first semiconductor device10amay be disposed on the first lead frame5aand connected with the second lead frame5bby wires. The second semiconductor device10bmay be disposed on the second lead frame5band connected with the third lead frame5cby wires. The third semiconductor device10cmay be disposed on the third lead frame5cand connected with the fourth lead frame5dby wires. The fourth semiconductor device10dmay be disposed on the fourth lead frame5dand connected with the fifth lead frame5eby wires.

Referring toFIG. 23, the semiconductor device package may include a body10including a cavity11, a semiconductor device100disposed inside the cavity11, and a light transmitting member50disposed on the cavity11.

The body10may be produced by processing an aluminum substrate. Accordingly, the body10according to an embodiment may have an inner surface and an outer surface, both of which have conductivity. Such a structure may have various benefits. When a non-conductive material such as AlN and Al2O3is used for the body10, a reflectivity for an ultraviolet wavelength band just ranges from 20% to 40%. Accordingly, there is a need to place a separate reflective member. Also, a separate circuit pattern and conductive member such as a lead frame may be needed. Accordingly, it is possible to increase a production cost and complicate a process. Also, a conductive member such as gold (Au) absorbs ultraviolet light, and thus there is a reduction in light extraction efficiency.

However, according to an embodiment, the body10itself is made of aluminum, and thus a separate reflective member may be omitted due to high reflectivity in an ultraviolet wavelength band. Also, the body10itself is conductive, and thus a separate circuit pattern and lead frame may be omitted. Also, since the body10is made of aluminum, the body10may have a good thermal conductivity ranging from 140 W/m·k to 160 W/m·k. Accordingly, it is possible to enhance heat emission efficiency.

The body10may include a first conductive part10aand a second conductive part10b. A first insulation part42may be disposed between the first conductive part10aand the second conductive part10b. Since both of the first conductive part10aand the second conductive part10bare conductive, the first insulation part42needs to be disposed in order to separate magnetic poles.

The body10may include a groove14disposed at an edge between a lower surface12and a side surface13and a second insulation part41disposed on the groove14. The groove14may be disposed along the edge between the lower surface12and the side surface13.

The second insulation part41may be made of the same material as that of the first insulation part42, but is not limited thereto. Each of the first insulation part42and the second insulation part41may be made of a material selected from among epoxy mold compounds (EMC), white silicon, photoimageable solder resist (PSR), silicon resin compositions, modified epoxy resin compositions such as a silicon-modified epoxy resin, modified silicon resin compositions such as an epoxy-modified silicon resin, polyimide resin compositions, modified polyimide resin compositions, polyphthalamide (PPA), polycarbonate resins, polyphenylene sulfide (PPS), liquid crystal polymers (LCP), acrylonitrile butadiene styrene (ABS) resins, phenolic resins, acrylic resins, and polybutylene terephthalate PBT resins.

According to an embodiment, the second insulation part41is disposed at a lower edge of the body10, and thus it is possible to prevent a burr from occurring at the edge when the package is cut. A burr may more frequently occur in an aluminum substrate than in other metal substrates. When a burr has occurred, the lower surface12may not be flat, causing a bad mounting. Also, when a burr has occurred, the thickness may become non-uniform and a measurement error may occur.

A third insulation part43may be disposed on the lower surface12of the body10and connected with the second insulation part41and the first insulation part42. According to an embodiment, the lower surface12of the body10, a lower surface of the second insulation part41, and a lower surface of the third insulation part43may be disposed on the same plane.

FIG. 24is a conceptual diagram of a light emitting structure according to an embodiment of the present invention, andFIG. 25is a graph showing the aluminum composition of the semiconductor structure according to an embodiment of the present invention.

Referring toFIG. 24, a semiconductor device according to an embodiment includes a light emitting structure120A including a first conductive semiconductor layer124, a second conductive semiconductor layer127, and an active layer126. Each semiconductor layer may have the same configuration as the structure described with respect toFIG. 1.

Referring toFIG. 25, the first conductive semiconductor layer124, the active layer126, a blocking layer129, and the second conductive semiconductor layer127may all contain aluminum.

Accordingly, the first conductive semiconductor layer124, the active layer126, the blocking layer129, and the second conductive semiconductor127may be made of AlGaN. However, the present invention is not limited thereto. Some of the layers may be made of GaN or AlN.

The active layer126may include a plurality of well layers126aand a plurality of barrier layers126b, which are alternately disposed therein. Each of the well layers126amay have an aluminum composition ranging from about 30% to about 50% in order to emit ultraviolet light. Each of the barrier layers127bmay have an aluminum composition ranging from 50% to 70% in order to trap carriers.

For example, a well layer closest to the blocking layer129among the well layers126ais defined as a first well layer126a, and the last barrier layer disposed between the first well layer126aand the blocking layer129is defined as a first barrier layer126b.

The blocking layer129may have an aluminum composition ranging from 50% to 90%. The blocking layer129may have a plurality of first blocking layers129dhaving a relatively high aluminum composition and a plurality of second layers129ahaving a relatively low aluminum composition, which are alternately disposed therein. When the aluminum composition of the blocking layer129is less than 50%, an energy barrier for blocking electrons may be insufficient in height, and the blocking layer129may absorb light emitted from the active layer126. When the aluminum composition of the blocking layer129is greater than 90%, the electrical characteristics of the semiconductor device may deteriorate.

Each of the first blocking layers129dmay have an aluminum composition ranging from 70% to 90%, and each of the second blocking layers129emay have an aluminum composition ranging from 50% to 70%. However, the present invention is not limited thereto, and the aluminum compositions of each first blocking layer129dand each second blocking layer129emay be appropriately adjusted.

A first intermediate layer S10may be disposed between the blocking layer129and the first well layer126aof the active layer126. The first intermediate layer S10may include a 3-1 section S11having an aluminum composition lower than the blocking layer129and a 3-2 section S12having an aluminum composition higher than the blocking layer129.

The first intermediate layer S10may be the first barrier layer126b. Accordingly, the first intermediate layer S10may have the same thickness as an adjacent barrier layer126b. For example, the first intermediate layer S10may have a thickness ranging from 2 nm to 10 nm. However, the present invention is not limited thereto, and the first intermediate layer S10may be a portion of the blocking layer129or a separate semiconductor layer disposed between the first barrier layer126band the blocking layer.

The 3-1 section S11may have an aluminum composition ranging from 50% to 70%. That is, the 3-1 section S11may be substantially the same aluminum composition as an adjacent barrier layer126b. The 3-1 section S11may have a thickness ranging from about 1 nm to about 8 nm. When the thickness of the 3-1 section is less than or equal to 1 nm, the aluminum composition of the well layer126arapidly increases, and thus it may be difficult to prevent a reduction of the crystallinity. Also, when the thickness of the 3-1 section S11is greater than 8 nm, it is possible to reduce injection efficiency of holes injected into the active layer126and thus reduce optical characteristics.

The 3-2 section S12may have a higher aluminum composition than the blocking layer129. The 3-2 section S12may have an aluminum composition increasing toward the blocking layer129. The aluminum composition of the 3-2 section S12may range from 80% to 100%. That is, the 3-2 section S12may be made of AlGaN or AIN. Alternatively, the 3-2 section S12may be a superlattice layer in which AlGaN and AlN are alternately disposed.

The 3-2 section S12may be thinner than the 3-1 section S11. The 3-2 section S12may have a thickness ranging from about 0.1 nm to about 4 nm. When the thickness of the 3-2 section S12is less than 0.1 nm, it may not be possible to block the movement of electrons. When the 3-2 section S12has a thickness greater than 4 nm, it is possible to reduce an efficiency with which holes are injected into the active layer.

A thickness ratio of the 3-1 section S11to the 3-2 section S12may range from 10:1 to 1:1. When the condition is satisfied, it is possible to reduce the hole injection efficiency while blocking the movement of electrons.

The 3-2 section S12may include an undoped section. Although the 3-2 section S12is grown without dopants supplied thereto, Mg of the blocking layer129may spread to a portion of the first section. However, in order to prevent spreading of dopants to the active layer126, at least some regions of the 3-2 section S12may include an undoped section.

FIG. 26is a graph showing an aluminum composition of a light emitting structure according to another embodiment of the present invention,FIG. 27is a graph obtained by measuring optical output power of a semiconductor device including a conventional light emitting structure, andFIG. 28is a graph obtained by measuring optical output power of a light emitting structure according to another embodiment of the present invention.

Referring toFIG. 26, the structure that has been described with reference toFIG. 25may be applied as it is, except for a second intermediate layer S20. The second intermediate layer S20may be a part of the blocking layer129, but is not limited thereto.

The second intermediate layer S20may have a lower aluminum composition than the blocking layer129and may have a higher aluminum composition than the 3-1 section S11. For example, the aluminum composition of the second intermediate layer S20may range from 50% to 80%.

The second intermediate layer S20may include a 4-1 section S21that does not contain a p-type dopant and a 4-2 section S22that contains a p-type dopant.

The 4-1 section S21may include an undoped section. Accordingly, it is possible to suppress spreading of dopants to the active layer126when the blocking layer129is grown. The 4-1 section S21may have a thickness ranging from 4 nm to 19 nm. When the thickness of the 4-1 section S21is less than 4 nm, it is possible to suppress spreading of dopants. When the thickness of the 4-1 section S21is greater than 19 nm, it is possible to reduce the hole injection efficiency.

The 4-2 section S22may contain a p-type dopant. The 4-2 section S22contains a dopant, and it is possible to improve efficiency with which holes are injected into the 4-1 section S21. That is, the 4-2 section S22may serve as a low-resistance layer for reducing a resistance level.

The 4-2 section S22may have a thickness ranging from 1 nm to 6 nm. When the thickness is less than 1 nm, it is difficult to effectively reduce resistance. When the thickness is greater than 6 nm, the thickness of the 4-1 section S21is reduced, and it may be difficult to suppress spreading of dopants. A ratio of the thickness of the 4-1 section S21to the thickness of the 4-2 section S22may range from 19:1 to 1:1.5.

However, the present invention is not limited thereto, and the second intermediate layer S20may have a superlattice structure in which the 4-1 section S21and the 4-2 section S22are alternately disposed.

Referring toFIG. 27, it can be seen that a semiconductor device having a conventional light emitting structure has optical output power reduced by 20% when about 100 hours pass. Also, it can be seen that the optical output power is reduced by 25% when about 500 hours pass.

On the other hand, referring toFIG. 28, it can be seen that a semiconductor device having the light emitting structure according to an embodiment has a luminous intensity reduced by about 3.5% when 100 hours pass and has almost the same optical output power even when about 500 hours pass. That is, it can be seen than optical output power is enhanced by about 20% without an intermediate layer according to an embodiment, compared to a conventional structure.

FIG. 29is a graph showing an aluminum composition of a light emitting structure according to still another embodiment of the present invention.

Referring toFIG. 29, the second conductive semiconductor layer129may include a 2-1 conductive semiconductor layer129aand a 2-2 conductive semiconductor layer129b.

The 2-1 conductive semiconductor layer127amay have a thickness greater than 10 nm and less than 200 nm. When the thickness of the 2-1 conductive semiconductor layer127ais less than 10 nm, resistance increases in a horizontal direction, and thus it is possible to reduce electric current injection efficiency. When the thickness of the 2-1 conductive semiconductor layer127ais greater than 200 nm, resistance increases in a vertical direction, and thus it is possible to reduce electric current injection efficiency.

The 2-1 conductive semiconductor layer127amay have a higher aluminum composition than the well layer126a. In order to generate ultraviolet light, the aluminum composition of the well layer126amay range from about 30% to about 50%. When the 2-1 conductive semiconductor layer127ahas a lower aluminum composition than the well layer126a, the 2-1 conductive semiconductor layer127aabsorbs light, and thus it is possible to reduce light extraction efficiency.

The 2-1 conductive semiconductor layer127amay have an aluminum composition greater than 40% and less than 80%. When the aluminum composition of the 2-1 conductive semiconductor layer127ais less than 40%, light may be absorbed. When the aluminum composition of the 2-1 conductive semiconductor layer127ais greater than 80%, electric current injection efficiency may deteriorate. For example, when the aluminum composition of the well layer126ais equal to 30%, the aluminum composition of the 2-1 conductive semiconductor layer127amay be equal to 40%.

The 2-2 conductive semiconductor layer127amay have a lower aluminum composition than the well layer126a. When the 2-2 conductive semiconductor layer127ahas a higher aluminum composition than the well layer126a, the 2-2 conductive semiconductor layer127ais unable to be sufficiently ohmic with a p-ohmic electrode due to an increase in resistance therebetween, and also it is possible to reduce electric current injection efficiency.

The aluminum composition of the 2-2 conductive semiconductor layer127amay be greater than 1% and less than 50%. When the aluminum composition is greater than 50%, the 2-2 conductive semiconductor layer127amay be unable to be sufficiently ohmic with a p-ohmic electrode. When the aluminum composition is less that 1%, the 2-2 conductive semiconductor layer127amay have a composition close to GaN and thus absorbs light.

The 2-2 conductive semiconductor layer127amay have a thickness greater than about 1 nm and less than about 30 nm. As described above, the 2-2 conductive semiconductor layer127ahas an aluminum composition low enough to be ohmic and thus may absorb ultraviolet light. Accordingly, it may be advantageous, in terms of optical output power, that the 2-2 conductive semiconductor layer127abe adjusted to be as thin as possible.

However, when the thickness of the 2-2 conductive semiconductor layer127ais controlled to be 1 nm or less, the 2-2 conductive semiconductor layer127amay not be disposed in some sections, and there may be a region in which the 2-1 conductive semiconductor layer127ais exposed outside the light emitting structure120. Also, when the thickness is greater than 30 nm, an absorbed quantity of light is so large that optical output power efficiency may decrease.

The 2-2 conductive semiconductor layer127amay further include a first sub-layer127eand a second sub-layer127d. The first sub-layer127emay be a surface layer in contact with the second electrode, and the second sub-layer127dmay be a layer for adjusting the aluminum composition.

The first sub-layer127emay have an aluminum composition greater than 1% and less than 20%. Alternatively, the aluminum composition may be greater than 1% and less than 10%.

When the aluminum composition is less than 1%, the first sub-layer127emay have a too high light absorption rate. When the aluminum composition is greater than 20%, contact resistance of the second electrode (i.e., the p-ohmic electrode) increases, and thus it is possible to reduce electric current injection efficiency.

However, the present invention is not limited thereto, and the aluminum composition of the first sub-layer127emay be adjusted in consideration of the electric current injection characteristics and the light absorption rate. Alternatively, the aluminum composition may be adjusted according to optical output power required by a product.

For example, when the electric current injection characteristics are more important than the light absorption rate, the aluminum composition may be adjusted in the range of 1% to 10%. When the optical output power characteristics are more important than the electrical characteristics in products, the aluminum composition of the first sub-layer127emay be adjusted in the range of 1% to 20%.

When the aluminum composition of the first sub-layer127eis greater than 1% and less than 20%, an operating voltage may decease due to a decrease in resistance between the first sub-layer127eand the second electrode. Accordingly, it is possible to enhance electrical characteristics. The first sub-layer127emay be formed to a thickness greater than 1 nm and less than 10 nm. Accordingly, it is possible to alleviate the light absorption problem.

The 2-2 conductive semiconductor layer127amay have a smaller thickness than the 2-1 conductive semiconductor layer127a. A thickness ratio of the 2-1 conductive semiconductor layer127ato the 2-2 conductive semiconductor layer127amay range from 1.5:1 to 20:1. When the thickness ratio is less than 1.5:1, the 2-1 conductive semiconductor layer127ais so thin that the electric current injection efficiency may decrease. When the thickness ratio is greater than 20:1, the 2-2 conductive semiconductor layer127ais so thin that there may be a reduction in ohmic reliability.

The 2-1 conductive semiconductor layer127amay have an aluminum composition decreasing away from the active layer126. Also, the 2-2 conductive semiconductor layer127amay have an aluminum composition decreasing away from the active layer126. Accordingly, the aluminum composition of the first sub-layer127emay satisfy the range of 1% to 10%.

However, the present invention is not limited thereto, and the aluminum compositions of the 2-1 conductive semiconductor layer127aand the 2-2 conductive semiconductor layer127amay include some sections in which there is no decrease, instead of continuously decreasing.

In this case, the 2-2 conductive semiconductor layer127amay have a greater reduction in aluminum composition than the 2-1 conductive semiconductor layer127a. That is, the 2-2 conductive semiconductor layer127amay have a greater variation in aluminum composition in a thickness direction than the 2-1 conductive semiconductor layer127a. Here, the thickness direction may refer to a direction from the first conductive semiconductor layer124to the second conductive semiconductor layer127or a direction from the second conductive semiconductor layer127to the first conductive semiconductor layer124.

The 2-1 conductive semiconductor layer127ahas a greater thickness than the 2-2 conductive semiconductor layer127aand has a higher aluminum composition than the well layer126a. Accordingly, the 2-1 conductive semiconductor layer127amay have a relatively gradual reduction in aluminum composition.

However, the 2-2 conductive semiconductor layer127ahas a small thickness and has a large variation in aluminum composition. Accordingly, the 2-2 conductive semiconductor layer127amay have a relatively high reduction in aluminum composition.

FIG. 30is a conceptual diagram of a light emitting structure grown on a substrate,FIG. 31is a diagram illustrating a substrate separation process,FIG. 32is a diagram illustrating a process of etching a light emitting structure, andFIG. 33is a diagram showing a manufactured semiconductor device.

Referring toFIG. 30, a buffer layer122, a light absorption layer123, a first conductive semiconductor layer124, an active layer126, a second conductive semiconductor layer127, a second electrode246, and a second conductive layer150may be sequentially formed on a growth substrate121.

In this case, a first intermediate layer and a second intermediate layer may be grown between the active layer126and the blocking layer129. A first barrier layer may be grown to have a 1-1 section having an aluminum composition ranging from 50% to 70% and a 1-2 section having an aluminum composition ranging from 80% to 100%. Also, a second intermediate layer may be grown to have a 2-1 section undoped with a p-type dopant and a 2-2 section doped with a dopant.

The light absorption layer123includes a first light absorption layer123ahaving a low aluminum composition and a second light absorption layer123bhaving a high aluminum composition. A plurality of first light absorption layer123aand a plurality of second light absorption layer123bmay be alternately disposed.

The first light absorption layer123amay have a lower aluminum composition than the first conductive semiconductor layer124. The first light absorption layer123amay be separated when absorbing laser light during a laser lift-off (LLO) process. Accordingly, it is possible to remove the growth substrate.

The thickness and aluminum composition of the first light absorption layer123amay be appropriately adjusted to absorb laser light having a predetermined wavelength (e.g., 246 nm). The aluminum composition of the first light absorption layer123amay range from 20% to 50%, and the thickness of the first light absorption layer123may range from 1 nm to 10 nm. For example, the first light absorption layer123amay be made of AlGaN, but is not limited thereto.

The second light absorption layer123bmay have a higher aluminum composition than the first conductive semiconductor layer124. The second light absorption layer123bmay enhance crystallinity of the first conductive semiconductor layer124, which is grown on the light absorption layer123, by increasing an aluminum composition that has been decreased by the first light absorption layer123a.

For example, the aluminum composition of the second light absorption layer123bmay range from 60% to 100%, and the thickness of the second light absorption layer123bmay range from 0.1 nm to 2.0 nm. The second light absorption layer123bmay be made of AlGaN or AlN.

In order to absorb laser light having a wavelength of 246 nm, the first light absorption layer123amay be thicker than the second light absorption layer123b. The thickness of the first light absorption layer123amay range from 1 nm to 10 nm, and the thickness of the second light absorption layer123bmay range from 0.5 nm to 2.0 nm.

A thickness ratio of the first light absorption layer123ato the second light absorption layer123bmay range from 2:1 to 6:1. When the thickness ratio is less than 2:1, the first light absorption layer123ais so thin that it may be difficult to sufficiently absorb laser light. When the thickness ratio is greater than 6:1, the second light absorption layer123bis so thin that the total aluminum composition of the light absorption layer may be reduced.

The light absorption layer123may have a total thickness greater than 100 nm and less than 400 nm. When the thickness is less than about 100 nm, the first light absorption layer123ais so thin that it is difficult to sufficiently absorb 246 nm laser light. When the thickness is greater than about 400 nm, the total aluminum composition is reduced and thus it is possible for the crystallinity to deteriorate.

According to an embodiment, it is possible to enhance the crystallinity by forming the light absorption layer123to have a superlattice structure. Due to such a structure, the light absorption layer123may function as a buffer layer for alleviating a lattice mismatch between the growth substrate121and the light emitting structure120.

Referring toFIG. 31, a step of removing the growth substrate121may include separating the growth substrate121by emitting laser L1from a side where the growth substrate121is present. The laser light L1may have a wavelength band absorbable by the first light absorption layer123a. As an example, the laser light may be KrF laser light having a wavelength band of 248 nm.

The growth substrate121and the second light absorption layer123bhave energy band gaps too high to absorb the laser light L1. However, the first light absorption layer123a, which has a low aluminum composition, may be disassembled by absorbing the laser light L1. Accordingly, it is possible to separate the first light absorption layer123atogether with the growth substrate121.

Subsequently, a residual light absorption layer123-2on the first conductive semiconductor layer124may be removed through a labeling process.

Referring toFIG. 32, after the second conductive layer150is formed over the second conductive semiconductor layer127, a plurality of recesses128may be formed to pass through up to a portion of the first conductive semiconductor layer124of the light emitting structure120. Subsequently, an insulation layer130may be formed at one side of the recesses128and over the second conductive semiconductor layer127. Subsequently, a first electrode142may be formed on a first conductive semiconductor layer124bexposed by the recesses128.

Referring toFIG. 33, a first conductive layer165may be formed under the insulation layer130. The first conductive layer165may be electrically insulated from the second conductive layer150by the insulation layer130.

Subsequently, a conductive substrate170may be formed under the first conductive layer165, and a second electrode pad166may be formed on a second conductive layer150exposed through a mesa etching process.

The semiconductor device may be applied to various kinds of light source devices. For example, conceptually, the light source devices may include a sterilizing device, a curing device, a lighting device, a display device, and a vehicle lamp. That is, the semiconductor device may be applied to various electronic devices for providing light by being disposed on housings thereof.

The sterilizing device may sterilize a desired region by having the semiconductor device according to an embodiment. The sterilizing device may be applied to home appliances such as water purifiers, air conditioners, and refrigerators, but is not limited thereto. That is, the sterilizing device may be applied to various products needing to be sterilized (e.g., medical apparatuses).

For example, a water purifier may sterilize circulating water by having the sterilizing device according to an embodiment. The sterilizing device may be placed at a nozzle or a discharging port through which water circulates and configured to emit ultraviolet light. In this case, the sterilizing device may include a water-proof structure.

The curing device may cure various kinds of liquids by having the semiconductor device according to an embodiment. Conceptually, the liquids may include various materials that are cured when ultraviolet light is emitted. For example, the curing device may cure various types of resins. Alternatively, the curing device may also be applied to cure beauty products such as manicure products.

The lighting device may include a light source module including a substrate and the semiconductor device according to an embodiment. The lighting device may further include a heat dissipation unit configured to dissipate heat of the light source module, and a power supply unit configured to process or convert an electric signal provided by an external source and provide the electric signal to the light source module. Also, the lighting device may include a lamp, a head lamp, or a streetlight.

The display device may include a bottom cover, a reflective plate, a light emitting module, a light guide plate, an optical sheet, a display panel, an image signal output circuit, and a color filter. The bottom cover, the reflective plate, the light emitting module, the light guide plate, and the optical sheet may constitute a backlight unit.

The reflective plate may be placed on the bottom cover, and the light emitting module may emit light. The light guide plate may be placed in front of the reflective plate to guide light emitted by the light emitting module forward. The optical sheet may include a prism sheet or the like and may be placed in front of the light guide plate. The display panel may be placed in front of the optical sheet. The image signal output circuit may supply an image signal to the display panel. The color filter may be placed in front of the display panel.

When the semiconductor device is used as a backlight unit of a display device, the semiconductor device may be used as an edge-type backlight unit or a direct-type backlight unit.

The semiconductor device may be a laser diode rather than the above-described light emitting diode.

Like the light emitting device, the laser diode may include a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer, which have the above-described structures. The laser diode may also utilize an electroluminescence phenomenon in which light is emitted when electric current flows after a p-type first conductive semiconductor and an n-type second conductive semiconductor are bonded with each other, but has a difference in directionality and phase of the emitted light. That is, the laser diode uses stimulated emission and constructive interference so that light having a specific single wavelength may be emitted at the same phase and in the same direction. Due to these characteristics, the laser diode may be used for an optical communication device, a medical device, a semiconductor processing device, or the like.

A light receiving device may include, for example, a photodetector, which is a kind of transducer configured to detect light and convert intensity of the light into an electric signal. The photodetector may include a photocell (silicon and selenium), an optical output element (cadmium sulfide and cadmium selenide), a photodiode (e.g., a PD with a peak wavelength in a visible blind spectral region or a true blind spectral region), a photo transistor, a photomultiplier, a photoelectric tube (vacuum and gas filling), an infra-red (IR) detector, or the like, but is not limited thereto.

Generally, a semiconductor device such as the photodetector may be produced using a direct bandgap semiconductor having good photoelectric transformation efficiency. Alternatively, the photodetector may have various structures. As the most common structure, the photodetector may include a pin-type photodetector using a p-n junction, a Schottky photodetector using a Schottky junction, a metal-semiconductor-metal (MSM) photodetector, or the like.

Like the light emitting device, the photodiode may include a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer, which have the above-described structures, and may be formed as a p-n junction or a pin structure. The photodiode operates when a reverse bias or a zero bias is applied. When light is incident on the photodiode, electrons and holes are generated such that electric current flows. In this case, the magnitude of electric current may be approximately proportional to intensity of light incident on the photodiode.

A photocell or a solar cell, which is a kind of photodiode, may convert light into electric current. Like the light emitting device, the solar cell may include a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer, which have the above-described structures.

Also, the solar cell may be used as a rectifier of an electronic circuit through rectification characteristics of a general diode using a p-n junction and may be applied to an oscillation circuit or the like of a microwave circuit.

Also, the above-described semiconductor device is not necessarily implemented only with semiconductors. Depending on the case, the semiconductor device may additionally include a metal material. For example, a semiconductor device such as the light receiving device may be implemented using at least one of Ag, Al, Au, In, Ga, N, Zn, Se, P, and As and may be implemented using an intrinsic semiconductor material or a semiconductor material doped with a p-type dopant or an n-type dopant.

While the present invention has been described with reference to exemplary embodiments, these are just examples and do not limit the present invention. It will be understood by those skilled in the art that various modifications and applications may be made therein without departing from the essential characteristics of the embodiments. For example, the elements described in the embodiments above in detail may be modified and implemented. Furthermore, differences associated with such modifications and applications should be construed as being included in the scope of the present invention defined by the appended claims.