The embodiment relates to a light-emitting device, a method of manufacturing the same, a light-emitting device package, and a lighting system. A light-emitting device according to the embodiment may include: a first conductive semiconductor layer; a gallium nitride-based superlattice layer on the first conductive semiconductor layer; an active layer on the gallium nitride-based superlattice layer; a second conductive gallium nitride-based layer on the active layer; and a second conductive semiconductor layer on the second conductive gallium nitride-based layer. The second conductive gallium nitride-based layer may include a second conductive GaN layer having a first concentration, a second conductive InxAlyGa(1-x-y)N (0<x<1, 0<y<1) layer having a second concentration and a second conductive AlzGa(1-z)N (0<z<1) layer having a third concentration on the active layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Phase of PCT/KR2013/009013 filed on Oct. 8, 2013, which claims priority under 35 U.S.C. 119(a) to Patent Application No. 10-2012-0111842 filed in the Republic of Korea on Oct. 9, 2012, all of which are hereby expressly incorporated by reference into the present application.

TECHNICAL FIELD

The embodiment relates to a light-emitting device, a method of manufacturing the same, a light-emitting device package, and a lighting system.

BACKGROUND ART

A light-emitting diode includes a P-N junction diode having a characteristic of converting electrical energy into light energy. The light-emitting device may include compound semiconductors belonging to group III and V on the periodic table. The light-emitting device can represent various colors by adjusting the compositional ratio of the compound semiconductors.

When forward voltage is applied to the light-emitting device, electrons of an N layer are combined with holes of a P layer, so that energy corresponding to an energy gap between a conduction band and a valance band may be generated. The energy is mainly emitted in the form of heat or light. In the case of the light-emitting device, the energy is generated in the form of light.

For example, a nitride semiconductor represents superior thermal stability and wide bandgap energy so that the nitride semiconductor has been spotlighted in the field of optical devices and high-power electronic devices. Specifically, blue light-emitting devices, green light-emitting devices, ultra-violet light-emitting devices, etc. using nitride semiconductors are commercialized and widely used.

Recently, as the demand for a high-efficiency light-emitting device is increased, the enhancement of light intensity has been issued.

In order to enhance the light, intensity, various attempts have been carried out to improve the structure of an active layer (MQW), an electron blocking layer (EBL), and a lower layer of the active layer, and good results are not obtained.

DISCLOSURE

Technical Problem

The embodiment relates to a light-emitting device, capable of enhancing light intensity, a method of manufacturing the same, a light-emitting device package, and a lighting system.

Technical Solution

A light-emitting device according to the embodiment may include: a first conductive semiconductor layer; a gallium nitride-based superlattice layer on the first conductive semiconductor layer; an active layer on the gallium nitride-based superlattice layer; a second conductive gallium nitride-based layer on the active layer; and a second conductive semiconductor layer on the second conductive gallium nitride-based layer, wherein the second conductive gallium nitride-based layer includes a second conductive GaN layer having a first concentration, a second conductive InxAlyGa(1-x-y)N (0<x<1, 0<y<1) layer having a second concentration and a second conductive AlzGa(1-z)N (0<z<1) layer having a third concentration on the active layer.

Advantageous Effects

According to the embodiment, the light-emitting device having the optimal structure capable of enhancing the light intensity, the method of manufacturing the same, the light-emitting device package, and the lighting system can be provided.

BEST MODE

Mode for Invention

Embodiment

FIG. 1is a sectional view showing a light-emitting device100according to a first embodiment.FIG. 2is a view showing an example of an energy band diagram of the light-emitting device100according to the first embodiment.FIG. 3is a partially enlarged energy band diagram B1of the light-emitting device according to the first embodiment.

The light-emitting device100according to the embodiment includes a first conductive semiconductor layer112, a gallium nitride-based superlattice layer124on the first conductive semiconductor layer112, an active layer114on the gallium nitride-based superlattice layer124, a second conductive gallium nitride-based layer129on the active layer114, and a second conductive semiconductor layer116on the second conductive gallium nitride-based layer129.

According to the embodiment, a light-emitting device having the optimal structure capable of improving light intensity is provided.

According to nitride-based compounds of the related art, the mobility of electrons is greater than that of holes. Accordingly, electrons pass a multi-quantum well structure faster than holes to reach a P type nitride semiconductor layer. In other words, the electrons may flow into the P type nitride semiconductor layer without being recombined with the holes. To prevent the phenomenon and confine the electrons within the multi-quantum well structure, an AlGaN-based electron blocking layer (EBL) is generally used.

However, since the AlGaN-based electron blocking layer has higher energy bandgap, the AlGaN-based electron blocking layer interrupts holes introduced into the multi-quantum well structure to increase forward voltage.

In the light-emitting device100according to the embodiment, the second conductive gallium nitride-based layer129may include a second conductive GaN layer126having a first concentration on the active layer, a second conductive InxAlyGa(1-x-y)N (0<x<1, 0<y<1) layer127having a second concentration and a second conductive AlzGa(1-z)N (0<z<1) layer128having a third concentration.

According to the embodiment, the lattice mismatch between the active layer114and the second conductive AlzGa(1-z)N layer128having the third concentration may be reduced by the second conductive InxAlyGa(1-x-y)N layer127having the second concentration, and the thermal dissociation of the active layer114can be prevented. The second conductive AlzGa(1-z)N layer128having the third concentration can more efficiently block electrons.

According to the first embodiment, the second conductive InxAlyGa(1-x-y)N layer127having the second concentration may be disposed closer to the active layer114than the second conductive AlzGa(1-z)N layer128having the third concentration.

Therefore, in the light-emitting device100according to the first embodiment, the second conductive GaN layer126having the first concentration may be disposed between the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration. In the embodiment, the first concentration is higher than the second concentration and the third concentration.

As described above, the second conductive GaN layer126having the first concentration is disposed between the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration in such a manner that the first concentration is higher than the second concentration and the third concentration, thereby solving a problem that doping concentration may not be increased in the process of forming the first conductive semiconductor layer112, the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration.

In other words, in the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration, as the composition of Al is increased, the bonding energy of AlN is increased so that the doping may be difficult. Therefore, the second conductive GaN layer126having the first concentration representing higher doping concentration is disposed between the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration to enhance the light intensity and lower the operating voltage.

In addition, as compared with when only both of the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration are used, when the second conductive GaN layer126having the first concentration is systematically bonded with the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration, the second conductive GaN layer126having the first concentration representing higher doping concentration can more sufficiently provide holes to the active layer114. Accordingly, the operating voltage of the light-emitting device is lowered, and an amount of heat emitted from the light-emitting device can be reduced.

The first embodiment, as shown inFIG. 3, may further include a secondary second conductive GaN layer126bhaving the first concentration disposed between the second conductive AlzGa(1-z)N layer128having the third concentration and the second conductive semiconductor layer116.

According the embodiment, a thickness of the second conductive AlzGa(1-z)N layer128having the third concentration may be between about 450 Å to 600 Å, but the embodiment is not limited thereto. When the thickness of the second conductive AlzGa(1-z)N layer128having the third concentration is less than 450 Å, a leakage current may increase, and when the thickness exceeds 600 Å, electrons may not be adequately supplied to the active layer114. A composition ratio of Al of the second conductive AlzGa(1-z)N layer128having the third concentration may be between 15% to 2.0%, but the embodiment is not limited thereto. When the composition ratio of Al of the second conductive AlzGa(1-z)N layer128having the third concentration is less than 15%, an optical efficiency is insufficiently improved, and when the composition ratio of Al of the second conductive AlzGa(1-z)N layer128having the third concentration exceeds 20%, the surface becomes blunt and a crystallizability may decrease.

According to the embodiment, when the second conductive AlzGa(1-z)N layer128having the third concentration has the thickness and the Al composition ratio, the supply of electrons to the active layer114increases and the leakage current reduces so the optical efficiency can be improved.

In the embodiment, the second conductive AlzGa(1-z)N layer128having the third concentration may have an energy bandgap equal to or higher than an energy bandgap of a quantum wall114bof the active layer and may include a primary second conductive AlzGa(1-z)N layer128ahaving the third concentration in which the energy bandgap is gradually decreased from the active layer114toward the second semiconductor layer116and a secondary second conductive AlzGa(1-z)N layer128bhaving the third concentration in which has an energy bandgap equal to or higher than the quantum wall114bon the primary second conductive AlzGa(1-z)N layer128ahaving the third concentration and in which the energy bandgap is gradually increased.

In the embodiment, a width of the secondary second conductive AlzGa(1-z)N layer128bhaving the third concentration may be wider than a width of the primary second conductive AlzGa(1-z)N layer128ahaving the third concentration. The embodiment may further include, a tertiary second conductive AlzGa(1-z)N layer128chaving the third concentration and in which a bandgap energy is constantly maintained on the secondary second conductive AlzGa(1-z)N layer128bhaving the third concentration.

According to the embodiment, a back diffusion of Mg to the active layer can be reduced by the primary second conductive AlzGa(1-z)N layer128ahaving the third concentration and in which the energy bandgap is gradually decreased, and an electron blocking is effectively performed to improve an optical extraction efficiency by the high Al composition of the secondary second conductive AlzGa(1-z)N layer128bhaving the third concentration.

FIG. 4is a sectional view showing a light-emitting device102according to a second embodiment,FIG. 5is a view showing an example of the energy-band diagram of the light-emitting device according to the second embodiment, andFIG. 6is a view showing a partially enlarged energy band diagram B2of the light-emitting device according to the second embodiment.

The first embodiment has the described effects, however, as shown inFIG. 2, when the second conductive GaN layer126having the first concentration is disposed between the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N having the third concentration, a hole transport obstacle region Q1may occur.

To solve the problem, in the light-emitting device according to the second embodiment, the second conductive InxAlyGa(1-x-y)N layer127having the second concentration may be disposed between the second conductive GaN layer126having the first concentration and the second conductive AlzGa(1-z)N layer128having the third concentration.

Accordingly, compared toFIG. 2in which the hole transport obstacle region Q1occurs, inFIG. 5, the hole transport can be adequately performed (Refer to Q2).

FIG. 7is a view showing a comparison of a luminous intensity of the light-emitting device according to the first embodiment and the second embodiment.

According to the second embodiment, when the second conductive InxAlyGa(1-x-y)N layer127having the second concentration is disposed between the second conductive GaN layer126having the first concentration and the second conductive AlzGa(1-z)N layer128having the third concentration, a transfer efficiency of a carrier (hole) is improved, as shown inFIG. 7, so the intensity of light E2in the second embodiment is improved compared to the intensity of light E1in the embodiment 1.

In addition, according to the second embodiment, when the second conductive InxAlyGa(1-x-y)N layer127having the second concentration is disposed between the second conductive GaN layer126having the first concentration and the second conductive AlzGa(1-z)N layer128having the third concentration, the transfer efficiency of a carrier (hole) is improved, so the intensity of light of the light-emitting chip according to the second embodiment may be improved compared to the intensity of light of the light-emitting according to the first embodiment.FIG. 8is a view showing a comparison of an inner quantum efficiency of the light-emitting device according to the first embodiment and the second embodiment.

According to the second embodiment, when the second conductive InxAlyGa(1-x-y)N layer127having the second concentration is disposed between the second conductive GaN layer126having the first concentration and the second conductive AlzGa(1-z)N layer128having the third concentration, the transfer efficiency of a carrier (hole) is improved, as shown inFIG. 8, so the inner quantum efficiency E2of the light-emitting device according to the second embodiment is improved compared to the inner quantum efficiency E1of the light-emitting device according to the first embodiment

FIG. 9is a sectional view of a light-emitting device103according to a third embodiment.FIG. 10is a view showing an example of an energy band diagram of the light-emitting device according to the third embodiment.

According to the third embodiment, the gallium nitride-based superlattice layer124may have a bandgap energy level which varies from the first conductive semiconductor layer112toward the active layer114.

For example, the bandgap energy level of the gallium nitride-based superlattice layer124may be reduced in the form of a step from the first conductive semiconductor layer112toward the active layer114, but the embodiment is not limited thereto.

For example, the gallium nitride-based superlattice layer124may include a first-group gallium nitride-based superlattice layer121having first bandgap energy at an area A adjacent to the first conductive semiconductor layer112and a second-group gallium nitride-based superlattice layer122having second bandgap energy lower than the first bandgap energy on the first-group gallium nitride-based superlattice layer121(area B).

In addition, the gallium nitride-based superlattice layer124may further include a third-group gallium nitride-based superlattice layer123having third bandgap energy provided on the second-group gallium nitride-based superlattice layer122at an area C adjacent to the active layer114.

The third bandgap energy may be equal to or lower than the second bandgap energy, but the embodiment is not limited thereto.

The gallium nitride-based superlattice layer124may include an InxGa1-xN/GaN (0<x<1) superlattice layer, and the difference D between a first bandgap energy level and a second bandgap energy level may be equal to or higher than a photon energy level of the gallium nitride-based superlattice layer.

For example, only when the difference (energy difference) of a well depth in the gallium nitride-based superlattice layer belonging to each group is equal to or higher than the phonon energy (about 88 meV) of InGaN, a portion of the energy of hot electrons may be transferred in the form of the phonon energy.

The gallium nitride-based superlattice layer124according to the embodiment may have at least two energy steps and the depth of a quantum well (multi-quantum well)114wof the active layer114is about 200 meV, so a plurality of energy steps can be provided and the number of the energy steps may be determined by dividing the depth of the quantum well by the minimum phonon energy.

According to the embodiment, the energy level of each group may be adjusted by adjusting the concentration of In contained in the well of each group.

For example, the concentration of In contained in the second-group gallium nitride-based superlattice layer122may be set to a value higher than that of In contained in the first-group gallium nitride-based superlattice layer121, thereby reducing the energy level of the second-group well122wto lower than the energy level of the first-group well121w.

According to the embodiment, hot electrons are cooled by the gallium nitride-based superlattice layer having a plurality of energy steps, so that a high-power light-emitting device having an effective electron injection layer can be provided.

According to the embodiment, the thickness of each group of the GaN-based superlattice layer may be controlled in order to enhance the electron injection efficiency by more efficiently cooling the hot electrons.

For example, the thickness of the first-group gallium nitride-based superlattice layer121may be thinner than the thickness of the second-group gallium nitride-based super lattice layer122.

In this case, the thickness of the first-group well121wprovided in the first-group gallium nitride-based superlattice layer121may be equal to the thickness of the first-group barrier121bprovided in the first-group gallium nitride-based superlattice layer121and the first-group well121wand the first-group barrier121bmay be prepared in a plurality of cycles. For example, the first-group well121wand the first-group barrier121bmay be controlled to have an equal thickness in the range of about 1 nm to 3 nm and may be prepared in a plurality of cycles so that the hot carriers can be effectively cooled as compared with a case where a single thick well and a single thick barrier are provided.

In addition, the second-group well122wand the second-group barrier122bprovided in the second-group gallium nitride-based superlattice layer122may be controlled to have an equal same thickness in the range of about 1 nm to 3 nm and may be prepared in a plurality of cycles so that the cooling of the hot carriers can be induced as compared with a case where a single thick well and a single thick barrier are provided.

In this case, the thickness of the second-group well122wmay be equal to the thickness of the first-group well121wand the thickness of the second-group barrier122bmay be equal to the thickness of the first-group barrier121b. Thus, even if the carriers recognize a predetermined energy barrier in the gallium nitride-based superlattice layer, the carriers may not be extinguished within the gallium nitride-based superlattice layer due to the well and the barrier having the regular thickness, so that the carriers can be smoothly injected.

According to the embodiment, the total thickness of the second-group gallium nitride-based superlattice layer122may be thicker than the total thickness of the first-group gallium nitride-based superlattice layer121. For example, the second-group gallium nitride-based superlattice layer122may include the second-group well122wand the second-group barrier122brepeatedly formed in about 8 to 12 cycles and the first-group gallium nitride-based superlattice layer121may include the first-group well121wand the first-group barrier121brepeatedly formed in about 3 to 5 cycles.

According to the embodiment, the hot carriers can be stably cooled for longer time in the second-group gallium nitride-based superlattice layer122that meets partially-cooled hot carriers rather than the first-group gallium nitride-based superlattice layer121that primarily meets the hot carriers, so the hot carriers may be efficiently cooled, thereby preventing the hot carriers from being overflowed.

In addition, according to the embodiment, the thickness of the third-group well123win the third-group gallium nitride-based superlattice layer123may be equal to the thickness of the second-group well122wand thinner than the thickness of the third-group barrier123b.

For example, the thickness of the third-group well123wmay be in the range of about 1 nm to about 3 nm, and the thickness of the third-group barrier123bmay be in the range of about 7 nm to about 11 nm, but the embodiment is not limited thereto.

According to the embodiment, the third-group barrier123bmay be adjacent to the active layer114, and the thickness of the third-group barrier123b, which is the final barrier, may be thicker than that of the barriers and wells of other groups.

According to the embodiment, the third-group barrier123bmay be doped with a first conductive element to improve the electron injection efficiency.

In addition, according to the embodiment, an undoped GaN layer125is further disposed between the third-group barrier123band the quantum well114wof the active layer114to prevent the first conductive element doped in the third-group barrier123bfrom diffusing into the active layer114and blocking the recombination for light emission.

According to the embodiment, hot electrons are cooled by the gallium nitride-based superlattice layer having a plurality of energy steps, so that a high-power light-emitting device having an effective electron injection layer can be provided.

A method of manufacturing the light-emitting device according the embodiment is described with reference toFIG. 11andFIG. 12.FIG. 11andFIG. 12describes the manufacturing method based on the third embodiment, however, the embodiment is not limited thereto.

Meanwhile,FIG. 12shows a lateral type light-emitting device, in which the light-emitting device103according to the third embodiment is grown on a predetermined growth substrate105, however the embodiment is not limited thereto, and may be employed in a vertical light-emitting device, in which an electrode is formed on a first conductive semiconductor layer exposed after the growth substrate is removed.

First, as shown inFIG. 11, in the light-emitting device according to the embodiment, a substrate105may include a material having excellent thermal conductivity, and may include a conductive substrate or an insulating substrate. For example, the substrate105may include at least one of sapphire (Al2O3), SiC, Si, GaAs, GaN, ZnO, GaP, InP, Ge, and Ga2O3.

According to the embodiment, a light reflection pattern is provided to enhance light extraction efficiency. For example, a patterned sapphire substrate (PSS) may be formed on the substrate105to enhance the light extraction efficiency.

In addition, according to the embodiment, a buffer layer107and an undoped semiconductor layer108are formed on the substrate105to reduce the lattice mismatch between a material of the light-emitting structure110and a material of the substrate105. For example, the buffer layer107may be formed of group III-V compound semiconductors, for example at least one of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, and AlInN, but the embodiment is not limited thereto.

Then, a first conductive semiconductor layer112is formed on the undoped semiconductor layer108. For example, the first conductive semiconductor layer112may include a semiconductor material having a compositional formula of InAlyGa1-x-yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1). In detail, the first conductive semiconductor layer112may include at least one of GaN, InN, AlN, InGaN, AlGaM, InAlGaM, AlInN, AlGaAs, InGaAs, AlInGaAs, GaP, AlGaP, InGaP, AlInGaP, and InP, but the embodiment is not limited thereto.

Next, the gallium nitride-based superlattice layer124may be formed on the first conductive semiconductor layer112. The gallium nitride-based superlattice layer124may effectively reduce the stress caused by lattice mismatch between the first conductive semiconductor layer112and the active layer114.

According to the embodiment, in an epi end, a light-emitting device having the optimal structure capable of improving light intensity is provided.

To this end, as shown inFIG. 10, in the embodiment, the gallium nitride-based superlattice layer124may have a bandgap energy level which varies from the first conductive semiconductor layer112toward the active layer114.

For example, the gallium nitride-based superlattice layer124may include a first-group gallium nitride-based superlattice layer121having first bandgap energy and a second-group gallium nitride-based superlattice layer122having second bandgap energy lower than the first bandgap energy on the first-group gallium nitride-based superlattice layer121.

In addition, the gallium nitride-based superlattice layer124may further include a third-group gallium nitride-based superlattice layer123having the third bandgap energy disposed on the second-group gallium nitride-based superlattice layer122.

The gallium nitride-based superlattice layer124may include an InxGa1-xN/GaN (0<x<1) superlattice layer, and the difference D between a first bandgap energy level and a second bandgap energy level may be equal to or higher than a photon energy level of the gallium nitride-based superlattice layer.

According to the embodiment, a growth temperature of a second group well122wof the second-group gallium nitride-based superlattice layer122may be higher than a growth temperature of a first-group well121wof the first-group gallium nitride-based superlattice layer121. For example, the first-group well121wmay be performed at a temperature equal to or lower than 500° C., and the second-group well (122w) may be grown at a temperature equal to or higher than about 900° C.

An entire growth temperature of the gallium nitride-based superlattice layer124may be performed at a temperature equal to or higher than 800° C.

According to the embodiment, an amount of indium (In) in each group well of the gallium nitride-based superlattice layer124may be controlled by controlling the growth temperature through a photo luminescence sub-peak position, but the embodiment is not limited thereto.

According to the embodiment, the energy level of each group may be adjusted by adjusting the concentration of In contained in the well of each group. For example, the concentration of In contained in the second-group gallium nitride-based superlattice layer122may be set to a value higher than that of In contained in the first-group gallium nitride-based superlattice layer121, thereby reducing the energy level of the second-group well122wto lower than the energy level of the first-group well121w.

According to the embodiment, hot electrons are cooled by the gallium nitride-based superlattice layer having a plurality of energy steps, so that a high-power light-emitting device having an effective electron injection layer can be provided.

In addition, according to the embodiment, the thickness of each group of the GaN-based superlattice layer may be controlled in order to enhance the electron injection efficiency by more efficiently cooling the hot electrons.

For example, the thickness of the first-group gallium nitride-based superlattice layer121may be thinner than the thickness of the second-group gallium nitride-based super lattice layer122.

In this case, the thickness of the first-group well121wprovided in the first-group gallium nitride-based superlattice layer121may be equal to the thickness of the first-group barrier121bprovided in the first-group gallium nitride-based superlattice layer121and the first-group well121wand the first-group barrier121bmay be prepared in a plurality of cycles. For example, the first-group well121wand the first-group barrier121bmay be controlled to have an equal thickness in the range of about 1 nm to 3 nm and may be prepared in a plurality of cycles so that the hot carriers can be effectively cooled as compared with a case where a single thick well and a single thick barrier are provided.

In addition, the second-group well122wand the second-group barrier122bprovided in the second-group gallium nitride-based superlattice layer122may be controlled to have an equal same thickness in the range of about 1 nm to 3 nm and may be prepared in a plurality of cycles so that the cooling of the hot carriers can be induced as compared with a case where a single thick well and a single thick barrier are provided.

In this case, the thickness of the second-group well122wmay be equal to the thickness of the first-group well121wand the thickness of the second-group barrier122bmay be equal to the thickness of the first-group barrier121b. Thus, even if the carriers recognize a predetermined energy barrier in the gallium nitride-based superlattice layer, the carriers may not be extinguished within the gallium nitride-based superlattice layer due to the well and the barrier having the regular thickness, so that the carriers can be smoothly injected.

According to the embodiment, the total thickness of the second-group gallium nitride-based superlattice layer122may be thicker than the total thickness of the first-group gallium nitride-based superlattice layer121.

According to the embodiment, the hot carriers can be stably cooled for longer time in the second-group gallium nitride-based superlattice layer122that meets partially-cooled hot carriers rather than the first-group gallium nitride-based superlattice layer121that primarily meets the hot carriers, so the hot carriers may be efficiently-cooled, thereby preventing the hot carriers from being overflowed.

In addition, according to the embodiment, the thickness of the third-group well123win the third-group gallium nitride-based superlattice layer123may be equal to the thickness of the second-group well122wand thinner than the thickness of the third-group barrier123b.

According to the embodiment, the third-group barrier123bmay be adjacent to the active layer114, and the thickness of the third-group barrier123b, which is the final barrier, may be thicker than that of the barriers and wells of other groups.

According to the embodiment, the third-group barrier123bmay be doped with a first conductive element to improve the electron injection efficiency. According to the embodiment, the third-group barrier123bmay be doped with high Si to improve the electron injection efficiency. For example, the third-group barrier123bmay be doped by Si equal to or higher than 19 cc, but the embodiment is not limited thereto.

In addition, according to the embodiment, an undoped GaN layer125is further disposed between the third-group barrier123band the quantum well114wof the active layer114to prevent the first conductive element doped in the third-group barrier123bfrom diffusing into the active layer114and blocking the recombination for light emission.

According to the embodiment, hot electrons are cooled by the gallium nitride-based superlattice layer having a plurality of energy steps, so that a high-power light-emitting device having an effective electron injection layer can be provided.

Then, the active layer114is formed on the gallium nitride-based superlattice layer124.

According to the embodiment, the active layer114may include at least one of a single quantum well structure, a multi quantum well (MQW) structure, a quantum wire structure, and a quantum dot structure.

For example, the active layer114may include the multi quantum well structure by injecting trimethylgallium gas (TMGa), ammonia gas (NH3), nitrogen gas (N2), and trimethylindium gas (TMIn), however, the embodiment is not limited thereto.

The well layer114w/barrier layer114bof the active layer114may include at least one of InGaN/InGaN, GaN/AlGaN, InAlGaN/GaN, GaAs(InGaAs)/AlGaAs, GaP(InGaP)/AlGaP pair structures, but the embodiment is not limited thereto. The well layer may be formed of material having a bandgap lower than a bandgap of the barrier layer.

The barrier layer114bmay be grown at a pressure of about 150 torr to 250 torr, and a temperature of about 700° C. to 800° C., however, the embodiment is not limited thereto.

Thereafter, in the embodiment, the second conductive gallium nitride-based layer129is formed on the active layer114.

According to the embodiment, a light-emitting device having the optimal structure capable of improving light intensity is provided.

According to the embodiment, the second conductive gallium nitride-based layer129may include, on the active layer114, the second conductive GaN layer126having the first concentration, the second conductive InxAlyGa(1-x-y)N (0<x<1, 0<y<1) layer127having the second concentration and the second conductive AlzGa(1-z)N (0<z<1) layer128having the third concentration.

According to the embodiment, the lattice mismatch between the active layer114and the second conductive AlzGa(1-x-y)N layer128having the third concentration may be reduced by the second conductive InxAlyGa(1-x-y)N layer127having the second concentration, and the thermal dissociation of the active layer114can be prevented. The second conductive AlzGa(1-z)N layer128having the third concentration can more efficiently block electrons.

According to the first embodiment, the second conductive InxAlyGa(1-x-y)N layer127having the second concentration may be disposed closer to the active layer114than the second conductive AlzGa(1-z)N layer128having the third concentration.

In the light-emitting device according to the first embodiment, the second conductive GaN layer126having the first concentration may be disposed between the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration. According to the embodiment, the first concentration is higher than the second concentration and the third concentration.

As described above, the second conductive GaN layer126having the first concentration is disposed between the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration in such a manner that the first concentration is higher than the second concentration and the third concentration, thereby solving a problem that doping concentration may not be increased in the process of forming the first conductive semiconductor layer112, the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration.

In other words, in the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration, as the composition of Al is increased, the bonding energy of AlN is increased so that the doping may be difficult. Therefore, the second conductive GaN layer126having the first concentration representing higher doping concentration is disposed between the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration to enhance the light intensity and lower the operating voltage.

In addition, as compared with when only both of the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration are used, when the second conductive GaN layer126having the first concentration is systematically bonded with the second conductive InxAlyGa(1-x-y)N layer127having the second concentration and the second conductive AlzGa(1-z)N layer128having the third concentration, the second conductive GaN layer126having the first concentration representing higher doping concentration can more sufficiently provide holes to the active layer114. Accordingly, the operating voltage of the light-emitting device is lowered, and an amount of heat emitted from the light-emitting device can be reduced.

The first embodiment, as shown inFIG. 3, may further include a secondary second conductive GaN layer126bof the first concentration disposed between the second conductive AlzGa(1-z)N layer128having the third concentration and the second conductive semiconductor layer116.

In the embodiment, a thickness of the second conductive AlzGa(1-z)N layer128having the third concentration may be between about 450 Å to 600 Å, but the embodiment is not limited thereto.

A composition ratio of Al of the second conductive AlzGa(1-z)N layer128having the third concentration may be between 15% to 20%, but the embodiment is not limited thereto. When the composition ratio of Al of the second AlzGa(1-z)N layer128having the third concentration is less than 15%, an optical efficiency is insufficiently-improved, and when the composition ratio of Al of the second conductive AlzGa(1-z)N layer128having the third concentration exceeds 20%, the surface becomes blunt and a crystallizability may decrease.

According to the embodiment, when the second conductive AlzGa(1-z)N layer128having the third concentration has the thickness and the Al composition ratio, the supply of electrons to the active layer114increases and the leakage current reduces so the optical efficiency can be improved.

In the embodiment, the second conductive AlzGa(1-z)N layer128layer having the third concentration may have an energy band gap equal to or higher than an energy bandgap of a quantum wall114bof the active layer and may include a primary second conductive AlzGa(1-z)N layer128ahaving the third concentration in which the energy bandgap is gradually decreased from the active layer114toward the second semiconductor layer116and a secondary second conductive AlzGa(1-z)N layer128bhaving the third concentration in which has an energy bandgap equal to or higher than the quantum wall114bon the primary second conductive AlzGa(1-z)N layer128ahaving the third concentration and in which the energy bandgap is gradually increased.

In the embodiment, a width of the secondary second conductive AlzGa(1-z)N layer128bhaving the third concentration may be wider than a width of the primary second conductive AlzGa(1-z)N layer128ahaving the third concentration. The embodiment may further include, a tertiary second conductive AlzGa(1-z)N layer128chaving the third concentration and in which a bandgap energy is constantly maintained on the secondary second conductive AlzGa(1-z)N layer128bhaving the third concentration.

According to the embodiment, a back diffusion of Mg to the active layer can be reduced by the primary second conductive AlzGa(1-z)N layer128having the third concentration and in which the energy bandgap is gradually decreased, and an electron blocking is effectively performed to improve an optical extraction efficiency by the high Al composition of the secondary second conductive AlzGa(1-z)N layer128having the third concentration.

In the light-emitting device according to the second embodiment, the second conductive InxAlyGa(1-x-y)N layer127having the second concentration may be disposed between the second conductive GaN layer126having the first concentration and the second conductive AlzGa(1-z)N layer128having the third concentration.

In the light-emitting device according to the second embodiment, the second conductive InxAlyGa(1-x-y)N layer127having the second concentration may be disposed between the second conductive GaN layer126having the first concentration and the second conductive AlzGa(1-z)N layer128having the third concentration.

Accordingly, compared toFIG. 2in which the hole transport obstacle region Q1occurs, inFIG. 5, the hole transport can be adequately performed (Refer to Q2).

According to the embodiment, the second conductive GaN layer126having the first concentration may be grown at a pressure of about 50 torr to 150 torr, and a temperature of about 850° C. to 940° C., but the embodiment is not limited thereto.

The second conductive InxAlyGa(1-x-y)N layer127may be grown at a pressure of about 150 torr to 250 torr, and a temperature of about 850° C. to 940° C., but the embodiment is not limited thereto.

The second conductive InxAlyGa(1-x-y)N layer127may have a composition ratio of Al in a range of about 7%˜11% and In in a range of about 1%˜4%, but the embodiment is not limited thereto.

Thereafter, the second conductive semiconductor layer116is formed on the second conductive gallium nitride-based layer129.

The second conductive semiconductor layer116may include a semiconductor compound. The second conductive semiconductor layer116may be realized by using groups III-V-II-VI compound semiconductors, and may be doped with second conductive type dopants.

For example, the second conductive semiconductor layer116may include a semiconductor material having a compositional formula of InxAlyGa1-x-yN (0≦x≦1, 0≦y≦1, and 0≦x+y≦1). If the second conductive semiconductor layer116is a P type semiconductor layer, the second conductive dopant, which serves as a P type dopant, may include Mg, Zn, Ca, Sr, or Ba.

Thereafter, the second conductive semiconductor layer116may be provided thereon with a transmissive electrode130. The transmissive electrode130may include a transmissive ohmic layer, and may be formed by laminating single metal, or by laminating a metal alloy and metal oxide in a multi-layer such that carrier injection may be efficiently performed.

According to the embodiment, the first conductive semiconductor layer112may include an N type semiconductor layer and the second conductive semiconductor layer116may include a P type semiconductor layer, but the embodiment is not limited thereto. In addition, a semiconductor layer, such as an N type semiconductor layer (not illustrated) having polarity opposite to that of the second conductive semiconductor layer116, may be formed on the second conductive semiconductor layer116. Thus, the light-emitting structure110may include one of an N-P junction structure, a P-N junction structure, an N-P-N junction structure, and a P-N-P junction structure.

Subsequently, as shown inFIG. 12, portions of the transmissive electrode130, the second conductive semiconductor layer116, the second conductive gallium nitride-based layer129, the active layer114, and the gallium nitride-based superlattice layer124may be removed to expose the first conductive semiconductor layer112.

Then, a second electrode132is formed on the transmissive electrode130, and a first electrode131is formed on the first conductive semiconductor layer112that is exposed.

According to the embodiment, the light-emitting device having the optimal structure capable of enhancing the light intensity, the method of manufacturing the same, the light-emitting device package, and the lighting system can be provided.

FIG. 13is a sectional view showing a light-emitting device package200having the light-emitting device according to the embodiments.

The light-emitting device package200according to the embodiment includes a package body205, third and fourth electrode layers213and214installed in the package body205, a light-emitting device100installed in the package body205and electrically connected with the third and fourth electrode layers213and214, and a molding member230to surround the light-emitting device100.

The package body205may include a silicon material, a synthetic resin material, or a metallic material. The package body205may have an inclination surface formed at a peripheral portion of the light-emitting device100.

The third and fourth electrode layers213and214are electrically isolated from each other and supply power to the light-emitting device100. In addition, the third and fourth electrode layers213and214may reflect light emitted from the light-emitting device100to increase the light efficiency, and discharge the light emitted from the light-emitting device100to the outside.

The light-emitting device100may include a lateral-type light-emitting device shown inFIGS. 1, 4, and 9, but the embodiment is not limited thereto. In other words, the light-emitting device may include a vertical type light-emitting device, or a flip-chip light-emitting device.

The light-emitting device may be installed in the package body205, or may be installed on the third electrode layer213or the fourth electrode layer214.

The light-emitting device100may be electrically connected with the third electrode layer213and/or the fourth electrode layer214through one of a wire scheme, a flip-chip scheme, or a die-bonding scheme. According to the embodiment, the light-emitting device100is electrically connected with the third electrode layer213through a wire230, and electrically connected with the fourth electrode layer214in the direct contact with the fourth electrode layer214for the illustrative purpose.

The molding member230may protect the light-emitting device100by surrounding the light-emitting device100. In addition, a phosphor232is included in the molding member230to change the wavelength of the light emitted from the light-emitting device100.

Light-emitting device packages according to the embodiment may be arrayed on a substrate, and a light guide plate, a prism sheet, a diffusion sheet, and a fluorescent sheet may be provided on the path of light emitted from the light-emitting device package. The light-emitting device package, the substrate, and the optical member may serve as a backlight unit or a lighting unit. For example, the lighting system may include a backlight unit, a lighting unit, an indication device, a lamp, and a street lamp.

FIGS. 14 to 16are views showing a lighting device including the light-emitting device according to the embodiment.

FIG. 14is a perspective view showing the lighting device according to the embodiment when viewed from the top of the lighting device.FIG. 15is a perspective view showing the lighting device according to the embodiment when viewed from the bottom of the lighting device.FIG. 16is an exploded perspective view showing the lighting device ofFIG. 14.

Referring toFIGS. 14 to 16, the lighting device according to the embodiment may include a cover2100, a light source module2200, a radiator2400, a power supply part2600, an inner case2700, and a socket2800. In addition, the lighting device according to the embodiment may further include at least one of a member2300and a holder2500. The light source module2200may include the light-emitting device100or the light-emitting device package according to the embodiment.

For example, the cover2100may have a blub shape, a hemisphere shape, a partially-open hollow shape. The cover2100may be optically coupled to the light source module2200. For example, the cover2100may diffuse, scatter, or excite light provided from the light source module. The cover2100may be a type of optical member. The cover2100may be coupled to the radiator2400. The cover2100may include a coupling part which is coupled to the radiator2400.

The cover2100may include an inner surface coated with a milk-white paint. The milk-white paint may include a diffusion material to diffuse light. The cover2100may have the inner surface of which surface roughness is greater than that of the outer surface thereof. The surface roughness is provided for the purpose of sufficiently scattering and diffusing the light from the light source module2200.

A material of the cover2100may include glass, plastic, polypropylene (PP), polyethylene (PE), and polycarbonate (PC). The polycarbonate (PC) has the superior light resistance, heat resistance and strength among the above materials. The cover2100may be transparent so that a user may view the light source module2200from the outside, or opaque. The cover2100may be formed through a blow molding scheme.

The light source module2200may be disposed at one surface of the radiator2400. Accordingly, the heat from the light source module2200is transferred to the radiator2400. The light source module2200may include a light source2210, a connection plate2230, and a connector2250.

The member2300is disposed at a top surface of the radiator2400, and includes guide grooves2310into which a plurality of light sources2210and the connector2250are inserted. The guide grooves2310correspond to a substrate of the light source2210and the connector2250.

A surface of the member2300may be coated with a light reflective material. For example, the surface of the member2300may be coated with white paint. The member2300again reflects light, which is reflected by the inner surface of the cover2100and is returned to the light source module2200, to the cover2100. Accordingly, the light efficiency of the lighting system according to the embodiment may be improved.

For example, the member2300may include an insulating material. The connection plate2230of the light source module2200may include an electrically conductive material. Accordingly, the radiator2400may be electrically connected to the connection plate2230. The member2300may be formed of an insulating material, thereby preventing the connection plate2230from being electrically shorted with the radiator2400. The radiator2400receives heat from the light source module2200and the power supply part2600and radiates the heat.

The holder2500covers a receiving groove2719of an insulating part2710of an inner case2700. Accordingly, the power supply part2600received in the insulating part2710of the inner case2700is closed. The holder2500includes a guide protrusion2510. The guide protrusion2510has a hole through a protrusion2610of the power supply part2600.

The power supply part2600processes or converts an electric signal received from the outside and provides the processed or converted electric signal to the light source module2200. The power supply part2600is received in the receiving groove of the inner case2700, and is closed inside the inner case2700by the holder2500.

The power supply part2600may include a protrusion2610, a guide part2630, a base2650, and an extension part2670.

The guide part2630has a shape protruding from one side of the base2650to the outside. The guide part2630may be inserted into the holder2500. A plurality of components may be disposed above one surface of the base2650. For example, the components may include a DC converter converting AC power provided from an external power supply into DC power, a driving chip controlling driving of the light source module2200, and an electrostatic discharge (ESD) protection device protecting the light source module2200, but the embodiment is not limited thereto.

The extension part2670has a shape protruding from an opposite side of the base2650to the outside. The extension part2670is inserted into an inside of the connection part2750of the inner case2700, and receives an electric signal from the outside. For example, a width of the extension part2670may be narrower than or equal to a width of the connection part2750of the inner case2700. Terminals of a “+ electric wire” and a “− electric wire” are electrically connected to the extension part2670and terminals of the “+ electric wire” and the “− electric wire” may be electrically connected to a socket2800.

The inner case2700may include a molding part therein together with the power supply part2600. The molding part is prepared by hardening molding liquid, and the power supply part2600may be fixed inside the inner case2700by the molding part.

According to the embodiment, the light-emitting device having the optimal structure capable of enhancing the light intensity, the method of manufacturing the same, the light-emitting device package, and the lighting system can be provided.