Light emitting diode, method of fabricating the same and LED module having the same

A light emitting diode is provided to include a first conductive-type semiconductor layer; a mesa including a second conductive-type semiconductor layer disposed on the first conductive-type semiconductor layer and an active layer interposed between the first and the second conductive-type semiconductor layers; and a first electrode disposed on the mesa, wherein the first conductive-type semiconductor layer includes a first contact region disposed around the mesa along an outer periphery of the first conductive-type semiconductor layer; and a second contact region at least partially surrounded by the mesa, the first electrode is electrically connected to at least a portion of the first contact region and at least a portion of the second contact region, and a linewidth of an adjoining region between the first contact region and the first electrode is greater than the linewidth of an adjoining region between the second contact region and the first electrode.

TECHNICAL FIELD

Exemplary embodiments of the disclosed technology relate to a light emitting diode (LED), an LED module including the same, and a method of fabricating the same. For example, some implementations of the disclosed technology relates to a light emitting diode having improved reliability, an LED module including the same, and a method of fabricating the same.

BACKGROUND

Since GaN-based light emitting diodes were first developed, GaN-based LEDs have been used for various applications including natural color LED displays, LED traffic signboards, white LEDs, and the like.

Generally, a GaN-based light emitting diode is formed by growing epitaxial layers on a substrate such as a sapphire substrate, and includes an N-type semiconductor layer, a P-type semiconductor layer and an active layer interposed therebetween. In addition, an n-electrode pad is formed on the N-type semiconductor layer and a p-electrode pad is formed on the P-type semiconductor layer. The light emitting diode is connected to an external power source through the electrode pads and driven thereby. In this case, current flows from the p-electrode pad to the n-electrode pad through the semiconductor layers.

On the other hand, a flip-chip type light emitting diode is used to prevent light loss due to the p-electrode pad while improving heat dissipation efficiency, and various electrode structures are proposed to promote current spreading in a large area flip-chip type light emitting diode. Examples are disclosed in U.S. Pat. No. 6,486,499. For example, a reflective electrode is formed on the P-type semiconductor layer, and extension legs are formed on a region of the N-type semiconductor layer, which is exposed by etching the P-type semiconductor layer and the active layer, to facilitate current spreading.

The reflective electrode formed on the P-type semiconductor layer reflects light generated from the active layer to improve light extraction efficiency and helps current spreading in the P-type semiconductor layer. On the other hand, the extension legs connected to the N-type semiconductor layer help current spreading in the N-type semiconductor layer to allow uniform generation of light in a wide active region. Particularly, a light emitting diode having a large area of about 1 mm2and used for high power output requires current spreading not only in the P-type semiconductor layer but also in the N-type semiconductor layer.

On the other hand, a forward voltage Vf is supplied to the light emitting diode to generate light, and a light emitting diode having good luminous efficacy refers to a light emitting diode capable of emitting the same intensity of light at a lower forward voltage. Therefore, various attempts have been made to decrease forward voltage of the light emitting diode.

On the other hand, in a process of dicing light emitting diodes on a wafer into individual light emitting diodes, an insulation layer exposed to a plane to be cut is likely to suffer from cracks. Such cracks can propagate into the light emitting diode. Moreover, interlayer delamination occurs due to cracks, thereby causing delamination of the insulation layer from semiconductor layers. Accordingly, moisture and contaminants can infiltrate the light emitting diode along an interface between the insulation layer and a semiconductor layer, thereby contaminating the light emitting diode, and delamination force with respect to layers in the light emitting diode can be reduced, thereby causing deterioration in reliability of the light emitting diode.

SUMMARY

Exemplary embodiments of the disclosed technology provide a light emitting diode chip having an electrostatic discharge protection function.

In addition, exemplary embodiments of the disclosed technology provide a light emitting diode which can be directly mounted on a printed circuit board or the like using a solder paste by preventing diffusion of metal elements from the solder paste.

Further, exemplary embodiments of the disclosed technology provide a light emitting diode having improved current spreading performance.

Furthermore, exemplary embodiments of the disclosed technology provide a light emitting diode having improved light extraction efficiency by improving reflectivity.

Furthermore, exemplary embodiments of the disclosed technology provide a light emitting diode a having low forward voltage.

Furthermore, exemplary embodiments of the disclosed technology provide a light emitting diode capable of simplifying a manufacturing process by reducing the use of photomasks, an LED module including the same, and a method of fabricating the same.

Furthermore, exemplary embodiments of the disclosed technology provide a light emitting diode having improved reliability and luminous efficacy by preventing damage to the light emitting diode due to cracks.

Additional features of the disclosed technology will be set forth in the description which follows, and in part will become apparent from the description, or may be learned from practice of the disclosed technology.

In one aspect, a light emitting diode includes: a first conductive-type semiconductor layer; a second conductive-type semiconductor layer; an active layer interposed between the first conductive-type semiconductor layer and the second conductive-type semiconductor layer; a first electrode pad region electrically connected to the first conductive-type semiconductor layer; a second electrode pad region electrically connected to the second conductive-type semiconductor layer; and a spark gap formed between a first leading end electrically connected to the first electrode pad region and a second leading end electrically connected to the second electrode pad region. The spark gap can achieve electrostatic discharge protection of the light emitting diode.

In some implementations, the light emitting diode may further include an upper insulation layer covering the second conductive-type semiconductor layer, the upper insulation layer including an opening that exposes the spark gap. As the spark gap is exposed to the outside, it is possible to prevent generation of static electricity by electrical sparks via air.

In some implementations, the light emitting diode may include a mesa placed on the first conductive-type semiconductor layer, the mesa including the active layer and the second conductive-type semiconductor layer, and the first electrode pad region may be electrically connected to the first conductive-type semiconductor layer at a side of the mesa.

In some implementations, the light emitting diode may further include a reflective electrode structure placed on the mesa; and a current spreading layer covering the mesa and the first conductive-type semiconductor layer, and having an opening that exposes the reflective electrode structure, the current spreading layer being electrically connected to the first conductive-type semiconductor layer while being insulated from the reflective electrode structure and the mesa, wherein the upper insulation layer covers the current spreading layer and the first leading end may be a portion of the current spreading layer.

In some implementations, the light emitting diode may further include an anti-diffusion reinforcing layer placed on the reflective electrode structure in the opening of the current spreading layer, wherein the second leading end may be a portion of the anti-diffusion reinforcing layer. In some implementations, the anti-diffusion reinforcing layer may be formed of the same material as that of the current spreading layer.

In some implementations, the upper insulation layer may include a first opening that exposes the current spreading layer to define the first electrode pad region, and a second opening that exposes the anti-diffusion reinforcing layer to define the second electrode pad region.

In some implementations, the light emitting diode may further include a lower insulation layer placed between the mesa and the current spreading layer and insulating the current spreading layer from the mesa, the lower insulation layer having an opening placed in an upper region of the mesa and exposing the reflective electrode structure.

In some implementations, the spark gap may be placed between the first electrode pad region and the second electrode pad region. The spark gap generates electric sparks when static electricity of high voltage is applied between the first electrode pad region and the second electrode pad region. To this end, a gap between the first leading end and the second leading end may be narrower than other portions. In some implementations, the first leading end and the second leading end may have a semi-circular or angled shape and face each other.

In another aspect, a method of fabricating a light emitting diode is provided to include: forming a first conductive-type semiconductor layer, an active layer and a second conductive-type semiconductor layer on a substrate; patterning the second conductive-type semiconductor layer and the active layer to form a mesa on the first conductive-type semiconductor layer; and forming a first electrode pad region electrically connected to the first conductive-type semiconductor layer and a second electrode pad region electrically connected to the second conductive-type semiconductor layer. Furthermore, the light emitting diode has a spark gap defined between the first leading end electrically connected to the first electrode pad region and the second leading end electrically connected to the second electrode pad region.

In some implementations, the method may further include: forming a reflective electrode structure on the second conductive-type semiconductor layer; and forming a current spreading layer covering the mesa and the first conductive-type semiconductor layer, and having an opening exposing the reflective electrode structure, the current spreading layer forming ohmic contact with the first conductive-type semiconductor layer while being insulated from the mesa, wherein the first leading end is a portion of the current spreading layer.

The current spreading layer allows uniform spreading of current in the first conductive-type semiconductor layer. The first leading end may be a portion of the current spreading layer.

In some implementations, the method may further include forming an anti-diffusion reinforcing layer on the reflective electrode structure, the anti-diffusion reinforcing layer being formed together with the current spreading layer, wherein the second leading end is a portion of the anti-diffusion reinforcing layer. Thus, the first and second leading ends can be formed together with the current spreading layer and the anti-diffusion reinforcing layer by the same process.

In some implementations, the method may further include forming an upper insulation layer covering the current spreading layer, the upper insulation layer having a first opening exposing the current spreading layer to define the first electrode pad region, and a second opening exposing the anti-diffusion reinforcing layer to define the second electrode pad region.

In some implementations, the upper insulation layer may further include an opening through which the first leading end and the second leading end are exposed. The opening may be distant from the first and second openings.

In some implementations, the method may further include forming a lower insulation layer covering the mesa and the first conductive-type semiconductor layer, before forming the current spreading layer, the lower insulation layer having openings that expose the reflective electrode structure and the first conductive-type semiconductor layer.

In some implementations, the lower insulation layer may include a silicon oxide layer and the upper insulation layer may include a silicon nitride layer.

In some implementations, the method may further include forming an anti-Sn diffusion plating layer on the first electrode pad region and the second electrode pad region using a plating technique.

In another aspect, a light emitting diode (LED) module is provided to comprise: a printed circuit board; and a light emitting diode bonded to an upper side of the printed circuit board, the light emitting diode comprising: a first conductive-type semiconductor layer; a mesa placed on the first conductive-type semiconductor layer and including an active layer and a second conductive-type semiconductor layer; a reflective electrode structure placed on the mesa; a current spreading layer covering the mesa and the first conductive-type semiconductor layer, and having an opening that exposes the reflective electrode structure, the current spreading layer being electrically connected to the first conductive-type semiconductor layer while being insulated from the reflective electrode structure and the mesa; and an upper insulation layer covering the current spreading layer, the upper insulation layer has a first opening exposing the current spreading layer to define the first electrode pad region, and a second opening exposing an exposed upper region of the reflective electrode structure to define the second electrode pad region, wherein the first electrode pad region and the second electrode pad region are bonded to corresponding pads on the printed circuit boards via solder pastes, respectively.

Since the first and second electrode pad regions are respectively defined by the first and second openings of the upper insulation layer, there is no need for a separate photomask for forming the first and second electrode pads.

In some implementations, the light emitting diode may further include an anti-Sn diffusion plating layer formed on the first electrode pad region and the second electrode pad region.

Unlike typical AuSn solders in the related art, the solder paste is a mixture of a metal alloy and an organic material and is cured by heat treatment to provide a bonding function. Thus, metal elements such as Sn in the solder paste are unlikely to diffuse, unlike metal elements in the typical AuSn solders in the related art.

The anti-Sn diffusion plating layer can prevent the metal elements such as Sn in the solder paste from diffusing into the light emitting diode. Furthermore, as the anti-Sn diffusion plating layer is formed by a plating technique such as electroless plating, there is no need for a separate photomask for formation of the plating layer.

In some embodiments, the light emitting diode may further include an anti-diffusion reinforcing layer placed on the reflective electrode structure in the opening of the current spreading layer, the anti-diffusion reinforcing layer being exposed through the second opening of the upper insulation layer. The anti-diffusion reinforcing layer can prevent metal elements such as Sn in the solder paste from diffusing to the reflective electrode structure in the light emitting diode.

In some implementations, the anti-diffusion reinforcing layer may be formed of the same material as that of the current spreading layer.

Thus, the anti-diffusion reinforcing layer may be formed together with the current spreading layer, and there is no need for a separate photomask for formation of the anti-diffusion reinforcing layer.

In some implementations, the current spreading layer may include an ohmic contact layer, a reflective metal layer, an anti-diffusion layer, and an anti-oxidation layer. In some implementations, the current spreading layer may form ohmic contact with the first conductive-type semiconductor layer through the ohmic contact layer. For example, the ohmic contact layer may be formed of Ti, Cr, Ni, and the like.

The reflective metal layer reflects light incident on the current spreading layer to increase reflectivity of the light emitting diode. The reflective metal layer may be formed of Al. In addition, the anti-diffusion layer prevents diffusion of metal elements and serves to protect the reflective metal layer. For example, the anti-diffusion layer can prevent diffusion of metal elements such as Sn in the solder paste. In some implementations, the anti-diffusion layer may include Cr, Ti, Ni, Mo, TiW, or W or combinations thereof. Each of Mo, TiW and W may be used to form a single layer. On the other hand, Cr, Ti, and Ni may be used to form a pair of layers.

In some implementations, the anti-diffusion layer may include at least two pairs of Ti/Ni or Ti/Cr layers. In some implementations, the anti-oxidation layer is formed to prevent oxidation of the anti-diffusion layer and may include Au.

In some implementations, the current spreading layer may have a reflectivity of 65% to 75%. Thus, the light emitting diode according to this embodiment of the invention can provide optical reflection by the current spreading layer in addition to optical reflection by the reflective electrode structure, whereby light traveling through a sidewall of the mesa and the first conductive-type semiconductor layer can be reflected.

In some implementations, the current spreading layer may further include a bonding layer placed on the anti-oxidation layer. In some implementations, the bonding layer may include Ti, Cr, Ni or Ta. The bonding layer is used to enhance bonding strength between the current spreading layer and the upper insulation layer.

In some implementations, the solder paste may adjoin the current spreading layer and the anti-diffusion reinforcing layer. Alternatively, the solder paste may adjoin the anti-Sn diffusion plating layer formed on the current spreading layer and the anti-diffusion reinforcing layer.

In some implementations, the reflective electrode structure may include a reflective metal section; a capping metal section; and an anti-oxidation metal section, the reflective metal section having a slanted side surface such that an upper surface of the reflective metal section has a narrower area than a lower surface thereof, and wherein a stress relief layer is formed at an interface between the reflective metal section and the capping metal section. The stress relief layer relieves stress due to a difference in coefficient of thermal expansion between the metal layers formed of different materials.

In some implementations, the mesa may include elongated branches extending parallel to each other in one direction, and a connecting portion at which the branches are connected to each other, and the opening of the current spreading layer may be placed on the connecting portion.

In some implementations, the light emitting diode may further include a lower insulation layer placed between the mesa and the current spreading layer and insulating the current spreading layer from the mesa, the lower insulation layer has an opening that is placed in an upper region of the mesa and exposes the reflective electrode structure.

In some implementations, the opening of the current spreading layer may have a greater width than the opening of the lower insulation layer such that the opening of the lower insulation layer is completely exposed therethrough. As a result, the current spreading layer can be insulated from the reflective electrode structure.

In some implementations, the light emitting diode may further include an anti-diffusion reinforcing layer placed within the opening of the current spreading layer and the opening of the lower insulation layer, and the anti-diffusion reinforcing layer may be exposed through the second opening of the upper insulation layer.

In some implementations, the lower insulation layer may include a silicon oxide layer and the upper insulation layer may include a silicon nitride layer. As the upper insulation layer is formed of silicon nitride, it is possible to prevent diffusion of metal elements from the solder paste through the upper insulation layer.

The light emitting diode may further include a substrate and a wavelength conversion layer covering a lower surface of the substrate. The substrate may be a growth substrate for growing the semiconductor layers. In addition, the wavelength conversion layer may cover the lower surface and a side surface of the substrate.

In another aspect, a light emitting diode is provided to comprise: a first conductive-type semiconductor layer; a mesa disposed on the first conductive-type semiconductor layer and comprising an active layer and a second conductive-type semiconductor layer; a reflective electrode structure disposed on the mesa; a current spreading layer covering the mesa and the first conductive-type semiconductor layer, and having an opening exposing the reflective electrode structure, the current spreading layer being electrically connected to the first conductive-type semiconductor layer while being insulated from the reflective electrode structure and the mesa; and an upper insulation layer covering the current spreading layer, the upper insulation layer having a first opening exposing the current spreading layer to define a first electrode pad region, and a second opening exposing an exposed upper region of the reflective electrode structure to define the second electrode pad region.

In some implementations, the light emitting diode further comprises: an anti-diffusion reinforcing layer disposed on the reflective electrode structure in the opening of the current spreading layer, wherein the anti-diffusion reinforcing layer is exposed through the second opening of the upper insulation layer, and is formed of the same material as that of the current spreading layer. In some implementations, the light emitting diode further comprises: anti-solder diffusion layers formed in the first opening and the second opening. In some implementations, the current spreading layer comprises an ohmic contact layer, a reflective metal layer, an anti-diffusion layer, and an anti-oxidation layer.

In another aspect, a method of fabricating a light emitting diode is provided. The method may include: forming a first conductive-type semiconductor layer, an active layer and a second conductive-type semiconductor layer on a substrate; patterning the second conductive-type semiconductor layer and the active layer to form a mesa on the first conductive-type semiconductor layer while forming a reflective electrode structure on the mesa to form ohmic contact with the mesa; forming a current spreading layer covering the mesa and the first conductive-type semiconductor layer, and having an opening that exposes the reflective electrode structure, the current spreading layer forming ohmic contact with the first conductive-type semiconductor layer while being insulated from the mesa; and forming an upper insulation layer covering the current spreading layer, the upper insulation layer having a first opening exposing the current spreading layer to define a first electrode pad region, and a second opening exposing an exposed upper region of the reflective electrode structure to define the second electrode pad region.

In the fabrication method, since there is no need for formation of electrode pads on the upper insulation layer, it is possible to reduce the number of photomasks for fabrication of the light emitting diode.

In some implementations, the method may further include forming an anti-diffusion reinforcing layer on the reflective electrode structure, wherein the anti-diffusion reinforcing layer can be formed together with the current spreading layer, and the second opening of the upper insulation layer can expose the anti-diffusion reinforcing layer. Accordingly, the reflective electrode structure can be concealed and protected by the anti-diffusion reinforcing layer and the upper insulation layer.

In some implementations, the method may further include forming a lower insulation layer covering the mesa and the first conductive-type semiconductor layer, before forming the current spreading layer; dividing the lower insulation layer and the first conductive-type semiconductor layer into chip regions by laser scribing; and patterning the lower insulation layer to form openings exposing the first conductive-type semiconductor layer and an opening exposing the reflective electrode structure.

Since a chip isolation region is formed using laser scribing, there is no need for use of a photomask. In addition, since laser scribing is performed after formation of the lower insulation layer, particles formed in the laser scribing process can be easily removed by cleaning the lower insulation layer, whereby the light emitting diode can be prevented from being contaminated by the particles.

In some implementations, the lower insulation layer may include a silicon oxide layer and the upper insulation layer may include a silicon nitride layer.

In some implementations, the method may further include forming an anti-Sn diffusion plating layer on the first electrode pad region and the second electrode pad region using a plating technique. The plating layer may be formed by electroless plating such as ENIG (electroless nickel immersion gold) and the like.

In some implementations, the substrate may be partially removed to have a small thickness by grinding and/or lapping. Then, the substrate is separated from the chip isolation region formed by laser scribing, thereby providing final individual chips separated from each other. Next, a wavelength conversion layer may be coated onto the light emitting diode chips, and the light emitting diode having the wavelength conversion layer is mounted on a printed circuit board via a solder paste, thereby providing an LED module.

The wavelength conversion layer may be formed by coating a phosphor-containing resin, followed by curing the resin. Alternatively, the wavelength conversion layer may be formed by spraying phosphor powder onto the light emitting diode chip using an aerosol apparatus.

In another aspect, a light emitting diode is provided to include: a first conductive-type semiconductor layer; a mesa including a second conductive-type semiconductor layer disposed over the first conductive-type semiconductor layer and an active layer interposed between the second conductive-type semiconductor layer and the first conductive-type semiconductor layer; and a first electrode disposed over the mesa, wherein the first conductive-type semiconductor layer includes a first contact region disposed around the mesa along an outer periphery of the first conductive-type semiconductor layer; and a second contact region at least partially surrounded by the mesa, the first electrode is electrically connected to at least a portion of the first contact region and at least a portion of the second contact region, and a linewidth of an adjoining region between the first contact region and the first electrode is greater than the linewidth of an adjoining region between the second contact region and the first electrode. With the structure wherein a contact area between the first electrode and the first conductive-type semiconductor layer through the first contact region is relatively increased as compared with a contact area between the first electrode and the first conductive-type semiconductor layer through the second contact region, the light emitting diode can have a reduced forward voltage (Vf). Furthermore, the light emitting diode can have improved luminous efficacy by more effectively spreading electric current in the horizontal direction.

In some implementations, the second contact region may be electrically connected to the first contact region. With this structure, the light emitting diode can have improved luminous efficacy by more effectively spreading electric current in the horizontal direction.

In some implementations, a length of the second contact region in a major axis direction may be 0.5 times or more the length of one side of the light emitting diode. With this structure, a contact area between the first electrode and the first conductive-type semiconductor layer can be increased, such that electric current flowing from the first electrode to the first conductive-type semiconductor layer can be more effectively dispersed, thereby further reducing forward voltage.

In some implementations, the linewidth of the adjoining region between the first contact region and the first electrode may be greater than 10 μm and the linewidth of the adjoining region between the second contact region and the first electrode may be 10 μm or less.

In some implementations, the light emitting diode may further include a first insulation layer interposed between the first electrode and the mesa, and the first insulation layer may partially expose the first contact region and the second contact region.

In some implementations, the first insulation layer may be restrictively disposed closer to the mesa than the adjoining region between the first contact region and the first electrode. With this structure, it is possible to increase the contact area between the first electrode and the first conductive-type semiconductor layer without decreasing a light emitting area. Furthermore, in a process of dicing light emitting diodes of a wafer into individual light emitting diodes, it is possible to prevent the first insulation layer disposed along the outer periphery of the first conductive-type semiconductor layer from suffering from cracking. Accordingly, it is possible to prevent delamination force of the first electrode or a second insulation layer described below from weakening due to infiltration of moisture or contaminants through the cracks, and to prevent contamination of the first electrode, thereby improving reliability of the light emitting diode.

In some implementations, the first electrode may contact the first contact region and the second contact region that are exposed through the first insulation layer while exposing an outer periphery of the first contact region.

In some implementations, a portion of the first conductive-type semiconductor layer not disposed under the first insulation layer may have a smaller thickness than a portion of the first conductive-type semiconductor layer disposed under the first insulation layer. A portion of an upper surface of the first conductive-type semiconductor layer is removed by etching, so that inert particles causing deterioration in conductivity and adhesion can be removed.

In some implementations, the first insulation layer disposed on an upper surface of the second conductive-type semiconductor layer may have the same thickness as the first insulation layer disposed on the upper surface of the first conductive-type semiconductor layer. Accordingly, it is possible to prevent infiltration of external contaminants into a lateral side of the mesa.

In some implementations, the light emitting diode may further include a second insulation layer covering the first electrode and the second contact region exposed through the first electrode.

In some implementations, the first electrode includes a plurality of layers, and an upper portion of the first electrode contacting the second insulation layer may include a Ti layer. With this structure, the light emitting diode has improved reliability through improvement in bonding strength between the first electrode and the second insulation layer.

In some implementations, the second insulation layer may include an opening exposing the first electrode, and an upper portion of the first electrode exposed through the opening of the second insulation layer may include an Au layer.

In some implementations, the light emitting diode may further include a first pad contacting the first electrode, wherein the first pad may contact the exposed Au layer. With this structure, the light emitting diode can exhibit improved bonding strength between the first pad and the first electrode and can reduce resistance.

In some implementations, the light emitting diode may further include a second electrode disposed on the second conductive-type semiconductor layer and electrically connected to the second conductive-type semiconductor layer, wherein the second electrode may be insulated from the first electrode by the first insulation layer.

In some implementations, a portion of the first insulation layer disposed on an upper surface of the second electrode may have a smaller thickness than a portion of the first insulation layer disposed on the upper surface of the second conductive-type semiconductor layer.

In some implementations, the second electrode includes a plurality of layers, and an upper portion of the second electrode contacting the first insulation layer may be a Ti layer. With this structure, the light emitting diode has improved bonding strength between the second electrode and the first insulation layer, thereby providing improved reliability.

In some implementations, the first insulation layer may include an opening exposing the second electrode, and an upper portion of the second electrode exposed through the opening of the first insulation layer may include an Au layer.

In some implementations, the light emitting diode may further include a second pad contacting the second electrode, and the second pad may contact the exposed Au layer. With this structure, the light emitting diode can exhibit improved bonding strength between the second pad and the second electrode and can reduce resistance.

In some implementations, the light emitting diode may further include a growth substrate disposed under the first conductive-type semiconductor layer.

In some implementations, the second insulation layer may cover an overall region of a side surface of the first conductive-type semiconductor layer and a portion of a side surface of the growth substrate. With this structure, the light emitting diode can protect the first conductive-type semiconductor layer from external moisture or impact, and can prevent an interface between the growth substrate and the first conductive-type semiconductor layer from splitting, thereby improving reliability.

In some implementations, the growth substrate may include at least one reformed region having a stripe shape and extending from at least one side surface of the growth substrate in a horizontal direction thereof. With this structure, the light emitting diode can have improved efficiency in extraction of light generated from the active layer.

In some implementations, the second insulation layer may be separated from the outer periphery of the first conductive-type semiconductor layer by a predetermined distance. Accordingly, it is possible to minimize damage to the second insulation layer in a process of dividing the wafer into individual light emitting diodes.

In some implementations, the mesa may include a plurality of protrusions protruding towards one side of the first conductive-type semiconductor layer; and a plurality of protrusions protruding towards the other side of the first conductive-type semiconductor layer. With this structure, not only in a region adjacent the one side of the first conductive-type semiconductor layer but also in a region adjacent the other side of the first conductive-type semiconductor layer, the light emitting diode can achieve efficient current flow between the second electrode disposed on the protrusions and the first electrode disposed on the second contact region. Accordingly, the region adjacent the other side of the first conductive-type semiconductor layer has improved luminous efficacy.

According to embodiments of the disclosed technology, it is possible to protect light emitting diodes from static electricity by forming a spark gap. In addition, some implementations of the disclosed technology provide a light emitting diode, which can prevent diffusion of metal elements from a solder paste, and a method for fabricating the same. Further, some implementations of the disclosed technology provide a light emitting diode having improved current spreading performance, for example, a flip-chip type light emitting diode having improved current spreading performance. Furthermore, the light emitting diodes according to some implementations of the disclosed technology have improved reflectivity by forming a current spreading layer, thereby providing improved light extraction efficiency. Furthermore, the light emitting diodes according to some implementations of the disclosed technology can omit a photolithography process for formation of electrode pads, and can reduce the number of photomasks by forming a chip isolation region using a laser scribing technique. Furthermore, electric current flowing from the first electrode to the first conductive-type semiconductor layer can efficiently spread, thereby reducing a forward voltage. Furthermore, the first electrode can be prevented from being contaminated due to cracks in the first insulation layer, thereby improving reliability of the light emitting diode.

DETAILED DESCRIPTION

In the related art, the light emitting diode employs linear extension legs which have high resistance, which results in imposing some limit on current spreading. Moreover, since the reflective electrode is placed only on the P-type semiconductor layer, a substantial amount of light is absorbed by the electrode pads and extension legs while not being reflected by the reflective electrode and thus, substantial light loss is caused. When used in a final product, the light emitting diode is provided by an LED module. The LED module generally includes a printed circuit board and an LED package mounted on the printed circuit board, in which the light emitting diode is mounted in chip form within the LED package. A typical LED chip is packaged after being mounted on a sub-mount, a lead frame or a lead electrode by silver pastes or AuSn solders. Then, the LED package is mounted on the printed circuit board by solder pastes. As a result, pads on the LED chip are distant from the solder pastes, and bonded to the printed circuit board by a relatively stable bonding material such as silver pastes, AuSn, and the like.

Recently, various attempts have been made to fabricate an LED module by directly bonding electrode pads of a light emitting diode to a printed circuit board using solder pastes. For example, an LED module can be fabricated by directly mounting an LED chip on a printed circuit board instead of packaging the LED chip. Otherwise, an LED module can be fabricated by mounting a so-called wafer level LED package on a printed circuit board. In these LED modules, since the electrode pads directly adjoin the solder pastes, metal elements such as tin (Sn) diffuse from the solder pastes into the light emitting diode through the pads and cause short circuit in the light emitting diode and device failure.

GaN-based compound semiconductors are formed by epitaxial growth on a sapphire substrate, the crystal structure and lattice parameter of which are similar to those of the semiconductors, in order to reduce crystal defects. However, the epitaxial layers grown on the sapphire substrate contain many crystal defects such as V-pits, threading dislocations, and the like. When high voltage static electricity is applied to the epitaxial layers, current is concentrated at crystal defects in the epitaxial layers, causing diode breakdown. Thus, with respect to electrostatic discharge or electrical fast transient (EFT), which is a spark generated in a switch, and lightning surge in air, securing reliability of LEDs becomes important.

Generally, in packaging of a light emitting diode, a Zener diode is mounted together with the light emitting diode to prevent electrostatic discharge. However, the Zener diode is expensive and a process of mounting the Zener diode increases the number of processes for packaging the light emitting diode and manufacturing costs. Moreover, since the Zener diode is placed near the light emitting diode in the LED package, the LED package has deteriorated luminous efficacy due to absorption of light by the Zener diode and deteriorated LED package yield.

Hereinafter, exemplary embodiments of the disclosed technology will be described in detail with reference to the accompanying drawings. It should be understood that the following embodiments are provided as some examples of the disclosed technology to facilitate understanding of the disclosed technology. Thus, it should be understood that the disclosed technology is not limited to the following embodiments and may be embodied in different ways. In addition, in the drawings, the width, length and thickness of components may be exaggerated for convenience. Further, it should be noted that the drawings are not to precise scale. Like components will be denoted by like reference numerals throughout the specification.

FIG. 1is a schematic sectional view of an LED module in accordance with one embodiment of the disclosed technology.

Referring toFIG. 1, an LED module according to an exemplary embodiment of the disclosed technology includes a printed circuit board51having pads53aand53band a light emitting diode100bonded to the printed circuit board51via solder pastes55.

The printed circuit board has a printed circuit thereon, and any substrate capable of providing an LED module can be used as the printed circuit board without limitation.

Conventionally, a light emitting diode is mounted on a substrate having a lead frame or lead electrodes formed thereon, and a light emitting diode package including such a light emitting diode is mounted on a printed circuit board. According to some implementations, the light emitting diode100is directly mounted on the printed circuit board51via the solder pastes55.

The light emitting diode100may include a flip-chip type light emitting diode and be mounted upside down on the printed circuit board. To this end, the light emitting diode100has a first electrode pad region43aand a second electrode pad region43b. The first and second electrode pad regions43aand43bmay be formed in a recess shape on one surface of the light emitting diode100.

On the other hand, a lower surface of the light emitting diode100, for example, a surface of the light emitting diode opposite the first and second electrode pad regions43aand43b, may be covered with a wavelength conversion layer45. The wavelength conversion layer45may cover not only the lower surface of the light emitting diode100but also side surfaces of the light emitting diode100.

InFIG. 1, the light emitting diode is schematically shown for convenience of description. The structure and respective components of the light emitting diode will be more clearly understood in the following description of a method of fabricating the light emitting diode. Furthermore, it should be noted that light emitting diodes according to embodiments of the disclosed technology are not limited to the structure in which the light emitting diode is directly mounted on the printed circuit board.

FIG. 2(a)toFIG. 10are views illustrating a method of fabricating a light emitting diode in accordance with an exemplary embodiment of the disclosed technology. In each feature, (a) is a plan view, (b) is a cross-sectional view taken along line A-A, and (c) is a cross-sectional view taken along line B-B.

First, referring toFIGS. 2(a) to 2(c), a first conductive-type semiconductor layer23, an active layer25and a second conductive-type semiconductor layer27are grown on a substrate21. The substrate100enables the growth of a GaN-based semiconductor layer, and may include, for example, a sapphire substrate, a silicon carbide substrate, a GaN substrate, or a spinel substrate, and the like. In some implementations, the substrate may be or include a patterned substrate such as a patterned sapphire substrate.

For example, the first conductive-type semiconductor layer may include an n-type gallium nitride-based layer and the second conductive-type semiconductor layer27may include a p-type gallium nitride-based layer. In addition, the active layer25may have a single quantum well structure or a multi-quantum well structure, and may include well layers and barrier layers. In addition, the composition of the well layers may be determined according to the wavelength of light and may include, for example, AlGaN, GaN or InGaN.

On the other hand, a pre-oxidation layer29may be formed on the second conductive-type semiconductor layer27. The pre-oxidation layer29may be formed of or include, for example, SiO2by chemical vapor deposition.

Then, a photoresist pattern30is formed. The photoresist pattern30is patterned to have openings30a. As shown inFIG. 2(a)andFIG. 2(b), the openings30aare formed such that an inlet of each opening has a narrower width than a bottom of the opening. The photoresist pattern30having the openings30aof this structure can be easily formed using a negative type photoresist.

Referring toFIGS. 3(a) to 3(c), the pre-oxidation layer29is etched using the photoresist pattern30as an etching mask. The pre-oxidation layer29may be etched by wet etching. As a result, the pre-oxidation layer29in the openings30aof the photoresist pattern30is etched to form openings29aof the pre-oxidation layer29, which expose the second conductive-type semiconductor layer27. The bottom portions of the openings29aare generally similar or greater than the bottom portions of the openings30aof the photoresist pattern30.

Referring toFIG. 4, a reflective electrode structure35is formed by a lift-off technology. The reflective electrode structure35may include a reflective metal section31, a capping metal section32and an anti-oxidation metal section33. The reflective metal section31includes a reflective layer, and a stress relief layer may be further formed between the reflective metal section31and the capping metal section32. The stress relief layer relieves stress due to difference in coefficient of thermal expansion between the reflective metal section31and the capping metal section32.

The reflective metal section31may be formed of or include, for example, Ni/Ag/Ni/Au, and may have an overall thickness of about 1600 Å. As shown, the reflective metal section31is formed to have a slanted side surface, for example, such that the bottom of the reflective metal section has a relatively wide area. Such a reflective metal section31may be formed by e-beam evaporation.

The capping metal section32covers upper and side surfaces of the reflective metal section31to protect the reflective metal section31. The capping metal section32may be formed by sputtering or by e-beam evaporation, for example, planetary e-beam evaporation, in which vacuum deposition is performed while rotating the substrate21in a slanted state. The capping metal section32may include Ni, Pt, Ti, or Cr, and may be formed by depositing, for example, about five pairs of Ni/Pt layers or about five pairs of Ni/Ti layers. Alternatively, the capping metal section32may include TiW, W, or Mo.

A material for the stress relief layer may be selected in various ways depending upon metal components of the reflective layer and the capping metal section32. For example, when the reflective layer is composed of or includes Al or Al-alloys and the capping metal section32is composed of or includes W, TiW or Mo, the stress relief layer may be or include a single layer of Ag, Cu, Ni, Pt, Ti, Rh, Pd or Cr, or a composite layer of Cu, Ni, Pt, Ti, Rh, Pd or Au. In addition, when the reflective layer is composed of or includes Al or Al-alloys and the capping metal section32is composed of or includes Cr, Pt, Rh, Pd or Ni, the stress relief layer may be or include a single layer of Ag or Cu, or a composite layer of Ni, Au, Cu or Ag.

In addition, when the reflective layer is composed of or includes Ag or Ag-alloys and the capping metal section32is composed of or includes W, TiW or Mo, the stress relief layer may be or include a single layer of Cu, Ni, Pt, Ti, Rh, Pd or Cr, or a composite layer of Cu, Ni, Pt, Ti, Rh, Pd, Cr or Au. Further, when the reflective layer is composed of or includes Ag or Ag-alloys and the capping metal section32is composed of or includes Cr or Ni, the stress relief layer may be or include a single layer of Cu, Cr, Rh, Pd, TiW or Ti, or a composite layer of Ni, Au or Cu.

Further, the anti-oxidation metal section33includes Au in order to prevent oxidation of the capping metal section32, and may be formed of or include, for example, Au/Ni or Au/Ti. Since Ti secures adhesion of an oxide layer such as SiO2, in some implementations, Ti can be used. The anti-oxidation metal section33may also be formed by sputtering or by e-beam evaporation, for example, planetary e-beam evaporation, in which vacuum deposition is performed while rotating the substrate21in a slanted state.

The photoresist pattern30is removed after deposition of the reflective electrode structure35, whereby the reflective electrode structure35remains on the second conductive-type semiconductor layer27, as shown inFIG. 4.

The reflective electrode structure35may include branches35band a connecting portion35a, as shown inFIG. 4. The branches35bmay have an elongated shape and be parallel to each other. The connecting portion35aconnects the branches35bto each other. However, it should be understood that the reflective electrode structure35is not limited to a particular shape and may be modified into various shapes.

Referring toFIG. 5, a mesa M is formed on the first conductive-type semiconductor layer21. The mesa M includes the active layer25and the second conductive-type semiconductor layer27. The active layer25is placed between the first conductive-type semiconductor layer23and the second conductive-type semiconductor layer27. The reflective electrode structure35is placed on the mesa M.

The mesa M is formed by patterning the second conductive-type semiconductor layer27and the active layer25so as to expose the first conductive-type semiconductor layer23. The mesa M may be formed to have a slanted side surface by photoresist reflow technology or the like. The slanted profile of the side surface of the mesa M enhances extraction efficiency of light generated in the active layer25.

As shown, the mesa M may include elongated branches Mb extending parallel to each other in one direction and a connection portion Ma connecting the branches to each other. With such configuration of the mesa, the light emitting diode can permit uniform spreading of electric current in the first conductive-type semiconductor layer23. Here, it should be understood that the mesa M is not limited to a particular shape and may be modified into various shapes. On the other hand, the reflective electrode structure35covers most of the upper surface of the mesa M and generally has the same shape as the shape of the mesa M in plan view.

While the second conductive-type semiconductor layer27and the active layer25are subjected to etching, the pre-oxidation layer29remaining on these layers is also partially removed by etching. On the other hand, although the pre-oxidation layer29can remain near an edge of the reflective electrode structure35on each of the mesa M, the remaining pre-oxidation layer29can also be removed by wet etching and the like. Alternatively, the pre-oxidation layer29may be removed before formation of the mesa M.

Referring toFIG. 6, after the mesa M is formed, a lower insulation layer37is formed to cover the mesa M and the first conductive-type semiconductor layer. The lower insulation layer37may be formed of or include an oxide layer such as SiO2and the like, a nitride layer such as SiNx and the like, or an insulation layer of MgF2by chemical vapor deposition (CVD) and the like. The lower insulation layer37may be a single layer or multiple layers. In addition, the lower insulation layer37may be or include a distributed Bragg reflector (DBR) in which low refractive index material layers and high refractive index material layers are alternately stacked one above another. For example, an insulating reflective layer having high reflectivity may be formed by stacking dielectric layers such as SiO2/TiO2, or SiO2/Nb2O5, and the like.

Then, a chip isolation region23his formed by laser scribing to divide the lower insulation layer37and the first conductive-type semiconductor layer23into chip units. Grooves may be formed on the upper surface of the substrate21by laser scribing. As a result, the substrate21is exposed near an edge of the first conductive-type semiconductor layer23.

Since the first conductive-type semiconductor layer23is divided into chip units by laser scribing, it is possible to omit a separate photomask for an isolation process. However, it should be understood that the disclosed technology is not limited to the isolation process using laser scribing. For example, the first conductive-type semiconductor layer23may be divided into chip units before or after formation of the lower insulation layer37using a typical photolithography and etching technique.

As shown inFIG. 6, the mesa M may be formed to be placed only inside an upper region of the first conductive-type semiconductor layer23. For example, the mesa M may be placed in an island shape on the upper region of the first conductive-type semiconductor layer23.

Next, referring toFIG. 7, the lower insulation layer37is subjected to patterning to form openings37aand37bin predetermined regions to allow electrical connection to the first conductive-type semiconductor layer23and the second conductive-type semiconductor layer27. For example, the lower insulation layer37may have openings37bwhich expose the first conductive-type semiconductor layer23, and openings37awhich expose the reflective electrode structure35.

The openings37aare placed only in upper regions of the mesas M, for example, on the connecting portions of the mesas M. The openings37bmay be placed in regions between the branches Mb of the mesas M and near the edge of the substrate21, and may have an elongated shape extending along the branches Mb of the mesas M.

Referring toFIG. 8, a current spreading layer39is formed on the lower insulation layer37. The current spreading layer39covers the mesa M and the first conductive-type semiconductor layer23. In addition, the current spreading layer39has an opening39aplaced in the upper region of the mesa M and exposing the reflective electrode structure35. The current spreading layer39may form ohmic contact with the first conductive-type semiconductor layer23through the opening37bof the lower insulation layer37. The current spreading layer39is insulated from the mesa M and the reflective electrodes35by the lower insulation layer37.

The opening39aof the current spreading layer39has a greater area than the opening37aof the lower insulation layer37to prevent the current spreading layer39from being connected to the reflective electrode structures35. Thus, the opening39ahas sidewalls placed on the lower insulation layer37.

The current spreading layer39is formed on an overall upper region of the substrate21excluding the openings39a. Thus, electric current can be easily dispersed through the current spreading layer39.

The current spreading layer39may include an ohmic contact layer, a reflective metal layer, an anti-diffusion layer, and an anti-oxidation layer. The current spreading layer can form ohmic contact with the first conductive-type semiconductor layer through the ohmic contact layer. For example, the ohmic contact layer may be formed of or include Ti, Cr, or Ni, and the like. The reflective metal layer increases reflectivity of the light emitting diode by reflecting incident light entering the current spreading layer. The reflective metal layer may be formed of or include Al. In addition, the anti-diffusion layer protects the reflective metal layer by preventing diffusion of metal elements. For example, the anti-diffusion layer can prevent diffusion of metal elements such as Sn within a solder paste. The anti-diffusion layer may be composed of or include Cr, Ti, Ni, Mo, TiW, or W or combinations thereof. The anti-diffusion layer may be a single layer including Mo, TiW or W. Alternatively, the anti-diffusion layer may include a pair of Cr, Ti or Ni layers. For example, the anti-diffusion layer may include at least two pairs of Ti/Ni or Ti/Cr layers. The anti-oxidation layer is formed to prevent oxidation of the anti-diffusion layer and may include Au.

The current spreading layer may have a reflectivity of 65% to 75%. Accordingly, the light emitting diode according to this embodiment can provide optical reflection by the current spreading layer in addition to optical reflection by the reflective electrode structure, whereby light traveling through the sidewall of the mesa and the first conductive-type semiconductor layer can be reflected.

The current spreading layer may further include a bonding layer placed on the anti-oxidation layer. The bonding layer may include Ti, Cr, Ni or Ta. The bonding layer is used to enhance bonding strength between the current spreading layer and the upper insulation layer, and may be omitted.

For example, the current spreading layer39may have a multi-layer structure including Cr/Al/Ni/Ti/Ni/Ti/Au/Ti.

While the current spreading layer39is formed, an anti-diffusion reinforcing layer40is formed on the reflective electrode structure35. The anti-diffusion reinforcing layer40and the current spreading layer39may be formed of or include the same material by the same process. The anti-diffusion reinforcing layer40is separated from the current spreading layer39. The anti-diffusion reinforcing layer40is placed within the opening39aof the current spreading layer39.

The anti-diffusion reinforcing layer40has a leading end40aextending therefrom, and the current spreading layer39has a leading end39bfacing the leading end40a. The leading end40amay be placed on the lower insulation layer37outside the opening37aof the lower insulation layer37. However, it should be understood that the disclosed technology is not limited thereto. Alternatively, the opening37aof the lower insulation layer37may have a similar shape to the shape of the leading end40a, and the leading end40amay be placed within the opening40aof the lower insulation layer37.

The leading end39aof the current spreading layer39is placed on the lower insulation layer37and is separated from the leading end40a. The leading end39band the leading end40adefine a spark gap therebetween. As a result, these leading ends39band40amay be placed closer than other portions or may have an angled shape in order to allow generation of an electric spark between the leading ends39band40awhen high voltage static electricity is applied to a gap between the current spreading layer39and the anti-diffusion reinforcing layer40. For example, as shown inFIG. 8, the leading ends39band40amay have a semi-circular shape or an angled shape and may be disposed to face each other.

Referring toFIG. 9, an upper insulation layer41is formed on the current spreading layer39. The upper insulation layer41has an opening41awhich exposes the current spreading layer39to define a first electrode pad region43a, and an opening41bwhich exposes the reflective electrode structure35to define a second electrode pad region43a. The opening41amay have an elongated shape perpendicular to the branches Mb of the mesa M. The opening41bof the upper insulation layer41has a narrower area than the opening39aof the current spreading layer39and thus the upper insulation layer41can cover the sidewall of the opening39a.

When the anti-diffusion reinforcing layer40is formed on the reflective electrode structure35, the opening41bexposes the anti-diffusion reinforcing layer40. In this case, the reflective electrode structure35can be concealed or sealed by the upper insulation layer41and the anti-diffusion reinforcing layer40. Furthermore, the upper insulation layer41has an opening41cwhich exposes at least part of the leading end39band the leading end40a. With this configuration, the spark gap between the leading end39band the leading end40ais exposed, thereby allowing generation of electrostatic discharge by an electrical spark through air.

Further, the upper insulation layer41may be formed on the chip isolation region23hto cover the side surface of the first conductive-type semiconductor layer23. With this configuration, it is possible to prevent penetration of moisture and the like through upper and lower interfaces of the first conductive-type semiconductor layer.

The upper insulation layer41may be formed of or include a silicon nitride layer to prevent diffusion of metal elements from solder pastes, and may have a thickness of 1 m to 2 m. When the thickness of the upper insulation layer is less than 1 m, it is difficult to prevent diffusion of metal the elements from the solder pastes.

Optionally, an anti-Sn diffusion plating layer (not shown) may be additionally formed on the first electrode pad region43aand the second electrode pad region43bby electroless plating such as ENIG (electroless nickel immersion gold) and the like.

The first electrode pad region43ais electrically connected to the first conductive-type semiconductor layer23through the current spreading layer39, and the second electrode pad region43bis electrically connected to the second conductive-type semiconductor layer27through the anti-diffusion reinforcing layer40and the reflective electrode structure35.

The first electrode pad region43aand the second electrode pad region43bare used to mount the light emitting diode on a printed circuit board and the like via solder pastes. Thus, in order to prevent short circuit between the first electrode pad region43aand the second electrode pad region43bby the solder pastes, electrode pads may be separated by a distance of about 300 m or more from each other.

Then, the substrate21may be removed to have a small thickness by partially grinding and/or lapping a lower surface of the substrate21. Then, the substrate21is divided into individual chip units, thereby providing divided light emitting diode chips. Here, the substrate21may be divided at the chip isolation region23hformed by laser scribing and thus there is no need for additional laser scribing for division of chips.

The substrate21may be removed from the light emitting diode chips before or after being divided into individual light emitting diode chip units.

Referring toFIG. 10, a wavelength conversion layer45is formed on the light emitting diodes separated from each other. The wavelength conversion layer45may be formed by coating a phosphor-containing resin onto the light emitting diodes using a printing technique, or by coating the substrate21with phosphor powder using an aerosol apparatus. For example, aerosol deposition can form a thin phosphor layer with a uniform thickness on the light emitting diodes, thereby improving color uniformity of light emitted from the light emitting diodes. As a result, the light emitting diodes according to the embodiments of the disclosed technology are completed and may be bonded to the corresponding pads53a,53bof the printed circuit board51by solder pastes, as shown inFIG. 1.

In this embodiment, the first and second electrode pad regions43aand43bexposed by the upper insulation layer41are directly mounted on the printed circuit board. However, it should be understood that the disclosed technology is not limited thereto. Alternatively, additional electrode patterns are formed on the electrode pad regions43aand43bto form further enlarged pad regions. In this case, however, an additional photomask for formation of the electrode patterns may be used.

FIG. 11(a)toFIG. 14(c)are views illustrating a method of fabricating a light emitting diode in accordance with another embodiment of the disclosed technology, and in each figure, (a) is a plan view, (b) is a cross-sectional view taken along line A-A, and (c) is a cross-sectional view taken along line B-B.

In the embodiments described above, the mesa M is formed after the reflective electrode structure35is formed. In the present implementations, the mesa M is formed before the reflective electrode structure35is formed.

First, referring toFIG. 11, as described with reference toFIG. 2, a first conductive-type semiconductor layer23, an active layer25and a second conductive-type semiconductor layer27are formed on a substrate21. Then, the mesa M is formed by a patterning process. The mesa M is similar to that described above inFIG. 5, and a detailed description thereof will be omitted.

Referring toFIG. 12, a pre-oxidation layer29is formed to cover the first conductive-type semiconductor layer23and the mesa M. The pre-oxidation layer29may be formed of or include the same material by the same process as those described with reference toFIG. 2. A photoresist pattern30having openings30ais formed on the pre-oxidation layer29. The openings30aof the photoresist pattern30are placed in an upper region of the mesa M. The photoresist pattern30is the same as that described with reference toFIG. 2except that the photoresist pattern30is formed on the substrate21having the mesa M formed thereon, and a detailed description thereof will be omitted.

Referring toFIG. 13, the pre-oxidation layer29is subjected to etching through the photoresist pattern30used as an etching mask, so that openings29aare formed to expose the second conductive-type semiconductor layer27therethrough.

Referring toFIG. 14, as described in detail with reference toFIG. 4, the reflective electrode structure35is formed on each mesas M by a lift-off technique. Then, light emitting diodes can be fabricated through similar processes to the processes described above with reference toFIG. 6toFIG. 11.

According to this embodiment, since the mesa M is formed prior to the reflective electrode structure35, the pre-oxidation layer29can remain on side surfaces of the mesas M and in regions between the mesas M. Then, the pre-oxidation layer29is covered by the lower insulation layer39and is subjected to patterning together with the lower insulation layer39.

FIG. 15is a plan view of a light emitting diode200in accordance with an embodiment of the disclosed technology,FIG. 16is a cross-sectional view taken along line A-B-B′-A′ ofFIG. 15,FIG. 17is a cross-sectional view taken along line C-C′ ofFIG. 15, andFIG. 18is an enlarged view of part I ofFIG. 16.

Referring toFIG. 15toFIG. 18, the light emitting diode200includes a first conductive-type semiconductor layer111, a mesa M including an active layer112and a second conductive-type semiconductor layer113, a first insulation layer130, a first electrode140, and a second insulation layer150, and may further include a growth substrate101and a second electrode120.

The growth substrate101may be selected from any substrate that allows growth of the first conductive-type semiconductor layer111, the active layer112and the second conductive-type semiconductor layer113thereon, and may include, for example, a sapphire substrate, a silicon carbide substrate, a gallium nitride substrate, an aluminum nitride substrate, or a silicon substrate, and the like. In some implementations, the growth substrate101may be or include a patterned sapphire substrate (PSS). The growth substrate101may include a slanted side surface, thereby improving extraction of light generated in the active layer112.

The second conductive-type semiconductor layer113may be disposed on the first conductive-type semiconductor layer111, and the active layer112may be interposed between the first conductive-type semiconductor layer111and the second conductive-type semiconductor layer113. The first conductive-type semiconductor layer111, the active layer112, and the second conductive-type semiconductor layer113may include III-V based compound semiconductors, for example, a nitride-based semiconductor such as (Al, Ga, In)N. The first conductive-type semiconductor layer111may include n-type dopants (for example, Si) and the second conductive-type semiconductor layer113may include p-type dopants (for example, Mg), or vice versa. The active layer112may include a multi-quantum well (MQM) structure. Upon application of forward bias to the light emitting diode200, light is emitted from the active layer112through recombination of electrons and holes therein. The first conductive-type semiconductor layer111, the active layer112, and the second conductive-type semiconductor layer113may be grown on the growth substrate101, for example, by metal organic chemical vapor deposition (MOCVD), molecular bean epitaxy (MBE), or the like.

The light emitting diode200may include at least one mesa M that includes the active layer112and the second conductive-type semiconductor layer113. Referring toFIG. 15, the mesa M may include a plurality of protrusions separated from one another. The light emitting diode200may include a plurality of mesas M separated from one another, without being limited thereto. The side surface of the mesa M may become a slanted side surface by a technology such as photoresist reflow, and the slanted side surface of the mesa M can improve luminous efficacy of light generated from the active layer112.

The first conductive-type semiconductor layer111may include a first contact region R1and a second contact region R2exposed through the mesa M. Since the mesa M is formed by removing the active layer112and the second conductive-type semiconductor layer113disposed on the first conductive-type semiconductor layer111, a portion excluding the mesa M becomes a contact region, which is an exposed upper surface of the first conductive-type semiconductor layer111. The first electrode140described below may be electrically connected to the first conductive-type semiconductor layer111by contacting the first contact region R1and the second contact region R2. The first contact region R1may be disposed around the mesa M along an outer periphery of the first conductive-type semiconductor layer111, specifically, along an outer periphery of the upper surface of the first conductive-type semiconductor layer between the mesa M and the side surface of the light emitting diode200. The second contact region R2may be at least partially surrounded by the mesa M. For example, referring toFIG. 15andFIG. 16, the first contact region R1may be disposed near side surfaces of the first conductive-type semiconductor layer111, and the second contact region R2may be disposed between the protrusions of the mesa M to be partially surrounded by the mesa M. Although not shown in the drawings, when the light emitting diode includes a plurality of mesas, the second contact region R2may be disposed between the plurality of mesas. Alternatively, the second contact region R1may be entirely surrounded by the mesa M. With this structure, the light emitting diode allows electric current to flow through the outer periphery and the center of the light emitting diode200, thereby enabling efficient current spreading.

A length of the second contact region R2in a major axis direction may be 0.5 times or more the length of one side of the light emitting diode200. With this structure, a contact area between the first electrode140and the first conductive-type semiconductor layer111can be increased such that electric current flowing from the first electrode140to the first conductive-type semiconductor layer111can be more efficiently spread, thereby further reducing forward voltage.

The first contact region R1and the second contact region R2may be formed by photolithography and etching. For example, an etching region is defined using a photoresist, and the first contact region R1and the second contact region R2may be formed by etching the second conductive-type semiconductor layer113and the active layer112using a dry etching process such as ICP.

The second electrode120is disposed on the second conductive-type semiconductor layer113and may be electrically connected to the second conductive-type semiconductor layer113. The second electrode120is formed on the mesa M and may have the same shape as the mesa M. The second electrode120may include a reflective metal layer121and may further include a barrier metal layer122, which covers an upper surface and a side surface of the reflective metal layer121. For example, the barrier metal layer122may be formed to cover the upper surface and the side surface of the reflective metal layer121by forming a pattern of the reflective metal layer121and then forming the barrier metal layer122thereon. For example, the reflective metal layer121may be formed by deposition and patterning of Ag, Ag alloy, Ni/Ag, NiZn/Ag, or TiO/Ag layer. In some implementations, the barrier metal layer122may be formed of or include Ni, Cr, Ti, Pt, or Au or combinations thereof, specifically, a combination layer formed of or including Ni/Ag/[Ni/Ti]2/Au/Ti sequentially stacked on an upper surface of the second conductive-type semiconductor layer113. In some implementations, at least a portion of the upper surface of the second electrode120may include a 300 Å thick Ti layer. With the structure wherein the upper surface of the second electrode120contacting the first insulation layer is composed of or includes the Ti layer, the light emitting diode200has improved bonding strength between the second electrode120and the first insulation layer130described below, thereby providing improved reliability. The reflective metal layer121prevents diffusion or contamination of a metallic material. Furthermore, the second electrode120may include a transparent conductive layer such as indium tin oxide (ITO), zinc oxide (ZnO), and the like. ITO is composed of or includes a metal oxide having high light transmittance and thus can improve luminous efficacy by suppressing absorption of light by the second electrode120. An electrode protective layer160may be disposed on the second electrode120. As described above with reference toFIG. 15andFIG. 16, the electrode protective layer160may be formed of or include the same material as the first electrode140, without being limited thereto.

The first insulation layer130may be disposed between the first electrode140and the mesa M. The first electrode140may be insulated from the mesa M through the first insulation layer130, and the first electrode140may be insulated from the second electrode120. The first insulation layer130may partially expose the first contact region R1and the second contact region R2. Specifically, the first insulation layer130may have an opening130a, through which the second contact region R2is partially exposed, and may cover only a portion of the first contact region R1between the outer periphery of the first conductive-type semiconductor layer111and the mesa M such that at least a portion of the first contact region R1is exposed. Referring toFIG. 15andFIG. 16, the first insulation layer130may be disposed along the outer periphery of the second contact region R2. At the same time, the first insulation layer130may be restrictively disposed close to the mesa M to be positioned more inward than an adjoining region between the first contact region R1and the first electrode140. Specifically, the first insulation layer130may be restrictively disposed more inside the light emitting diode200rather than the adjoining region between the first contact region R1and the first electrode140. With this structure, the light emitting diode can have an increased contact area between the first electrode140and the first conductive-type semiconductor layer111without decreasing a light emitting area. Furthermore, in a process of dicing light emitting diodes200on a wafer into individual light emitting diodes200, the first insulation layer130disposed along the outer periphery of the first conductive-type semiconductor layer111can be prevented from cracking. Accordingly, it is possible to prevent delamination force of the first electrode140or a second insulation layer150described below from weakening due to infiltration of moisture or contaminants through cracks, and to prevent contamination of the first electrode, thereby improving reliability of the light emitting diode200. The first insulation layer130may have an opening130bexposing the second electrode120described below. The second electrode120may be electrically connected to a pad or bump through the opening130b.

As shown inFIG. 18, the first insulation layer130may include a preliminary insulation layer131and a main insulation layer132.

The preliminary insulation layer131may be formed on the upper surface of the mesa (m) and the first conductive-type semiconductor layer111so as to cover at least a region in which the second electrode120will be formed and at least a portion of an exposed region of the first conductive-type semiconductor layer111. Furthermore, the preliminary insulation layer131may further cover the side surface of the mesa M and may partially cover the upper surfaces of the mesas M. The preliminary insulation layer131may contact the second electrode120or may be separated therefrom. In the structure wherein the preliminary insulation layer131is separated from the second electrode120, the second conductive-type semiconductor layer113may be partially exposed between the preliminary insulation layer131and the second electrode120. The preliminary insulation layer131may include SiO2, SiNx, or MgF2, and the like. Further, the preliminary insulation layer131may include multiple layers, or a distributed Bragg reflector in which materials having different indices of refraction are alternately stacked one above another.

In some implementations, the preliminary insulation layer131may be formed before formation of the second electrode120, after formation of the second electrode120, or during formation of the second electrode120. For example, when the second electrode120includes a conductive oxide layer and a reflective layer disposed on the conductive oxide layer and including a metal, the preliminary insulation layer131may be formed after formation of the conductive oxide layer on the second conductive-type semiconductor layer225and before formation of the reflective layer. At this time, the conductive oxide layer forms ohmic contact with the second conductive-type semiconductor layer225and the preliminary insulation layer131may be formed to a thickness of 400 Å to 2000 Å. In other implementations, the preliminary insulation layer131may be formed before formation of the second electrode120. In these implementations, the second electrode120forms ohmic contact with the second conductive-type semiconductor layer113and may include a reflective layer formed of or including a metallic material. In these implementations, since the preliminary insulation layer131is formed before formation of the reflective layer including a metallic material, it is possible to prevent reduction in reflectivity of the reflective layer and increase in resistance due to interdiffusion of materials between the reflective layer and a light emitting structure220. Furthermore, it is possible to prevent short circuit due to remaining materials on a portion at which the second electrode120is not formed during formation of the reflective layer including a metallic material.

The main insulation layer132may be disposed to cover the preliminary insulation layer131. The main insulation layer132may be formed by a suitable deposition method such as PECVD, or e-beam evaporation, and the like. The main insulation layer132may be formed in a shape as shown inFIG. 12through patterning after being formed to cover the entirety of the first conductive-type semiconductor layer111, the mesa M and the second electrode120. Patterning may include photolithographic etching or lift-off. The main insulation layer132may include SiO2, SiNx, or MgF2, and the like. Furthermore, the main insulation layer132may include multiple layers, or a distributed Bragg reflector in which materials having different indices of refraction are alternately stacked one above another. Further, the main insulation layer132may be thicker than the preliminary insulation layer131, and may have a thickness of, for example, 1,000 Å to 18,000 Å.

As described above, the first insulation layer130may be formed in a shape as shown inFIG. 15toFIG. 18by etching. At this time, during etching, a portion of the upper surface of the second electrode120is removed such that the second electrode120has a reduced thickness. Specifically, the surface of the second electrode120exposed through the opening130bof the first insulation layer130can be removed to a predetermined thickness by etching. More specifically, the Ti layer including the exposed surface of the second electrode120can be removed by etching. Accordingly, an adjoining region between the upper surface of the second electrode120and the first insulation layer130can maintain good bonding strength through the remaining Ti layer, which is not removed and corresponds to a portion of the upper surface of the second electrode120contacting the first insulation layer130. At the same time, in other regions of the second electrode120to which external current is applied, connection resistance can be lowered due to removal of the Ti layer, whereby the light emitting diode can have a reduced forward voltage.

After the first insulation layer130is formed in a shape as shown inFIG. 15toFIG. 18by etching, the exposed upper surface of the first conductive-type semiconductor layer111may be additionally etched. Specifically, after formation of the main insulation layer132, regions of the first contact region R1and the second contact region R2not covered by the first insulation layer130may be etched. Accordingly, a portion of the first conductive-type semiconductor layer111not disposed under the first insulation layer130may have a smaller thickness than a portion of the first conductive-type semiconductor layer111disposed under the first insulation layer130. Furthermore, particles derived from inert gas such as CF4and the like used in etching of the first insulation layer130and remaining on the exposed region of the first conductive-type semiconductor layer111can be removed. Accordingly, bonding strength between the first electrode140and the first conductive-type semiconductor layer111can be improved and contact resistance between the first electrode140and the first conductive-type semiconductor layer111can be reduced.

Referring toFIG. 18, since the preliminary insulation layer131is not disposed on the second electrode120and extends from the upper surface of the second conductive-type semiconductor layer113to cover a portion of the upper surface of the first conductive-type semiconductor layer111, thickness130T1of the first insulation layer130disposed on the upper surface of the second electrode120may be smaller than thickness130T2of the first insulation layer130disposed on the upper surface of the second conductive-type semiconductor layer113. Further, the thickness130T2of the first insulation layer130disposed on the upper surface of the second conductive-type semiconductor layer113may be the same as thickness130T3of the first insulation layer130disposed on the upper surface of the first conductive-type semiconductor layer111. Accordingly, with the structure wherein the first insulation layer130can cover the side surface of the mesa M without decreasing the thickness thereof, the light emitting diode can prevent infiltration of external contaminants while preventing damage to the first insulation layer130on the side surface of the mesa M.

The first electrode140may be disposed on the first insulation layer130. Specifically, the first electrode140may cover most of the first insulation layer130. The first electrode140may adjoin at least a portion of the first contact region R1and at least a portion of the second contact region R2. With this structure, the first electrode140can be electrically connected to the first conductive-type semiconductor layer111. The first electrode140may expose an outer periphery of the first contact region R1. Referring toFIG. 15andFIG. 16, the adjoining region between the first contact region R1and the first electrode140may be disposed closer to the mesa M than the adjoining region between the first contact region R1and the second insulation layer150described below. Specifically, the adjoining region between the first contact region R1and the first electrode140may be disposed further inside the light emitting diode200than the adjoining region between the first contact region R1and the second insulation layer150described below. In this structure, since the first electrode140is not exposed from a side surface of the light emitting diode200, the first electrode140can be effectively protected from external moisture and the like. Furthermore, the first electrode140may adjoin a portion of the second contact region R2and an interface between the first electrode140and the second contact region R2may be a linear plane.

A first linewidth L1, which is a linewidth of the adjoining region between the first contact region R1and the first electrode140, may be greater than a second linewidth L2, which is a linewidth of the adjoining region between the second contact region R2and the first electrode140. In this structure, a contact area between the first electrode140and the first conductive-type semiconductor layer111through the first contact region R1is relatively increased and the light emitting diode200can have a reduced forward voltage. Furthermore, the light emitting diode allows more efficient current spreading in the horizontal direction, thereby improving luminous efficacy. Specifically, the first linewidth L1may be greater than 10 μm and the second linewidth L2may be 10 μm or less. For example, the first linewidth L1may be 11 μm and the second linewidth L2may be 10 μm.

As shown in the drawings, the first electrode140may be disposed on the second electrode120described below through the opening130b, as in one example of the electrode protective layer160. At the same time, the first electrode140contacting the first contact region R1and the second contact region R2may be electrically insulated from the electrode protective layer160on the second electrode120by the second insulation layer150described below. In this structure, when solders composed of AuSn or the like are used for electrical connection, the first electrode140can prevent the solders from diffusing into the second electrode120and a step between the first electrode140and the second electrode120can be reduced, thereby allowing the light emitting diode200to be more stably attached to a circuit member such as a printed circuit board.

The first electrode140may include a highly reflective metal layer such as an Al layer, and the highly reflective metal layer may be formed on a bonding layer such as a Ti, Cr or Ni layer. Furthermore, a protective layer composed of or including a single layer or multiple layers of Ni, Cr, or Au, and the like may be formed on the highly reflective metal layer. The first electrode140may have a multilayer structure of, for example, Cr/Ti/Al/Ti/Ni/Au. Specifically, the first electrode140may be or include a laminate layer of Cr/Al/[Ti/Ni]2/Ti/Ni/Au/Ti sequentially stacked on the first conductive-type semiconductor layer111. More specifically, an upper surface of the first electrode140may include a 100 Å thick Ti layer. With the structure wherein the upper surface of the first electrode140is composed of or including the Ti layer, the light emitting diode200can have improved bonding strength between the first electrode140and the second insulation layer150described below, thereby providing improved reliability. The first electrode140may be formed through deposition and patterning of a metallic material.

The second insulation layer150may adjoin a portion of the first contact region R1. Specifically, the second insulation layer150may cover a portion of the first contact region R1exposed through the first electrode140. Further, the second insulation layer150may cover at least a portion of the first electrode140. The second insulation layer150may have an opening150aexposing the first electrode140and an opening150bexposing the second electrode120described below. In the structure wherein the light emitting diode200includes the electrode protective layer160, the second insulation layer150may be interposed between the first electrode140and the electrode protective layer160. Accordingly, insulation between the first electrode140and the electrode protective layer160can be further secured. The second insulation layer150may be formed by depositing an oxide insulation layer, a nitride insulation layer, or a polymer such as polyimide, Teflon® or Parylene on the first electrode140, followed by patterning.

The second insulation layer150may be formed by a suitable deposition method such as PECVD, or e-beam evaporation, and the like. The second insulation layer150may be formed in a shape as shown inFIG. 15toFIG. 18through patterning after being formed to cover the entirety of the first conductive-type semiconductor layer111and the first electrode140. Patterning may include photolithographic etching or lift-off.

During patterning of the second insulation layer150, a portion of the upper surface of the first electrode140is removed such that the first electrode140has a reduced thickness. Specifically, the surface of the first electrode140exposed through the openings150a,150bof the second insulation layer150can be removed to a predetermined thickness by etching. More specifically, the Ti layer including the exposed surface of the second electrode140can be removed by etching. Accordingly, an adjoining region between the upper surface of the first electrode140and the second insulation layer150can maintain good bonding strength through the remaining Ti layer, which is not removed and corresponds to a portion of the upper surface of the first electrode140contacting the second insulation layer150. At the same time, in other regions of the first electrode140connected to an external electrode via solders and the like, connection resistance can be lowered due to removal of the Ti layer, whereby the light emitting diode can have a reduced forward voltage. The second insulation layer150may cover an overall area of a side surface of the first conductive-type semiconductor layer111and a portion of a side surface of the growth substrate101. With this structure, the light emitting diode200can protect the first conductive-type semiconductor layer111from external moisture or impact and can prevent an interface between the growth substrate101and the first conductive-type semiconductor layer111from splitting, thereby providing improved reliability.

The second insulation layer150may cover at least a portion of the slanted side surface of the growth substrate101. With this structure, the second insulation layer150can be effectively attached to the growth substrate101, thereby increasing delamination force while improving reliability of the light emitting diode200. The slanted surface may be formed in the course of allowing a laser beam to enter the growth substrate in the process of dicing a wafer into individual light emitting diodes200.

FIG. 19is a sectional view of a light emitting diode in accordance with an embodiment of the disclosed technology and a circuit member on which the light emitting diode is mounted,FIG. 20is an enlarged sectional view of part I2ofFIG. 19,FIG. 21is an enlarged sectional view of part I3ofFIG. 20, andFIG. 22is a sectional view illustrating a structure wherein the light emitting diode in accordance with an embodiment of the disclosed technology is mounted on a circuit member.

Referring toFIG. 19, a plurality of light emitting diodes200may be mounted on a circuit member300and may be used as a single module. The circuit member300may include a printed circuit board (PCB), without being limited thereto. As shown inFIG. 19, the circuit member300may include a base310and interconnection lines321and322, but is not limited to the shape shown inFIG. 19.

Referring toFIG. 20, the light emitting diode200may be mounted on the circuit member through pads170and180. Specifically, the pads170and180may be interposed between the light emitting diode200and the interconnection lines321and322of the circuit member. The pads170and180may include solders or a eutectic metal, without being limited thereto. Specifically, AuSn may be used as the eutectic metal.

Additionally referring toFIG. 21, the pads170and180may contact the first electrode140and the second electrode120, respectively or if the electrode protective layer160is disposed on the second electrode120, the pads170and180may contact the first electrode140and the electrode protective layer160, respectively. Since the Ti layer140aexposed through the first electrode140and the second electrode120is removed by etching upon formation of the first insulation layer130and the second insulation layer150, the pads170and180can contact the first electrode140and the second electrode120, respectively, from which the Ti layer140ais removed. Specifically, since the Ti layer140ais removed from the first electrode140and the second electrode120, an Au layer140bcan be exposed to contact the pads170and180. Further, in the structure wherein the electrode protective layer160is disposed on the second electrode120and is formed of or includes the same material as the first electrode140, the Ti layer of the electrode protective layer160may also be removed, such that the exposed Au layer contacts the pad180.

Referring toFIG. 22, the pads170and180may include a eutectic metal. In this implementation, the pads170and180may be formed of or include an Au-containing material, for example, AuSn. Accordingly, since Au components of the pads170and180can contact the first electrode140and the second electrode120, or the first electrode140and the Au layer of the electrode protective layer160, bonding strength between the light emitting diode200and the pads170,180can be increased. Accordingly, the circuit member having the light emitting diode200mounted thereon can have improved reliability.

FIG. 23is a plan view of a light emitting diode201in accordance with an embodiment of the disclosed technology,FIG. 24is a cross-sectional view taken along line A-B-B′-A′ ofFIG. 23, andFIG. 25is a side view of the light emitting diode201ofFIG. 23. The light emitting diode201shown inFIG. 23is similar to the light emitting diode200described with reference toFIG. 15toFIG. 18except that the light emitting diode201includes a second insulation layer150separated from an outer periphery of a first conductive-type semiconductor layer111and a growth substrate101includes at least one reformed region101R.

Specifically, the growth substrate101may include at least one reformed region101R that extends from at least one side surface of the growth substrate101in the horizontal direction and has a stripe shape. The reformed region101R may be formed in the process of providing individual light emitting diodes through division of the growth substrate101. For example, the reformed region101R may be formed through internal machining of the growth substrate. A scribing plane may be formed inside the growth substrate101by internal laser machining. At this time, a distance from the reformed region101R to a lower surface of the growth substrate101may be smaller than a distance from the reformed region101R to an upper surface of the growth substrate101. Considering light emitted through the side surface of the light emitting diode201, laser machining is performed mainly with respect to a lower side of the growth substrate101such that the reformed region101R is formed relatively close to the lower side thereof, thereby improving efficiency in extraction of light generated from the active layer112. Furthermore, when the reformed region101R is formed near the first conductive-type semiconductor layer111, there can be a problem in terms of electrical characteristics due to damage to a nitride semiconductor during laser machining. Accordingly, with the structure wherein the reformed region101R is formed relatively close to the lower side of the growth substrate101, it is possible to prevent deterioration in reliability and luminous efficacy of the light emitting diode201due to damage to the nitride-based semiconductor.

The second insulation layer150may be disposed to be separated from the outer periphery of the first conductive-type semiconductor layer111. Specifically, the second insulation layer150may be disposed in other regions excluding the side surface of the first conductive-type semiconductor layer111and the side surface of the growth substrate101, and may be separated a predetermined distance from the outer periphery of the first conductive-type semiconductor layer111. Accordingly, it is possible to prevent damage to the first insulation layer150due to stress applied to interfaces between individual light emitting diodes during the process of providing the individual light emitting diodes through division of the growth substrate101.

FIG. 26is a plan view of a light emitting diode202in accordance with an embodiment of the disclosed technology andFIG. 27is a cross-sectional view taken along line A-B-B′-A′ ofFIG. 26.

The light emitting diode202shown inFIG. 26andFIG. 27is similar to the light emitting diode200described with reference toFIG. 15andFIG. 16except that the adjoining region between the first contact region R1and the first electrode140is disposed along the outer periphery of the overall upper surface of the first conductive-type semiconductor layer. Specifically, the adjoining region between the first contact region R1and the first electrode140may be disposed near all four side surfaces of the first conductive-type semiconductor layer111and may completely surround the mesa M. In this embodiment, a contact area between the first electrode140and the first conductive-type semiconductor layer111can be increased such that electric current flowing from the first electrode140to the first conductive-type semiconductor layer111can be more efficiently spread, thereby further reducing forward voltage.

FIG. 28is a plan view of a light emitting diode203in accordance with an embodiment of the disclosed technology,FIG. 29is a cross-sectional view taken along line A-A′ ofFIG. 28, andFIG. 30is a cross-sectional view taken along line B-B′ ofFIG. 28.

The light emitting diode203shown inFIG. 28toFIG. 30is similar to the light emitting diode200described with reference toFIG. 15andFIG. 16excluding the shape of the mesa M.

Specifically, the mesa M of the light emitting diode200shown inFIG. 15andFIG. 16includes the plurality of protrusions protruding towards one side surface of the light emitting diode200by way of example. On the contrary, the light emitting diode203shown inFIG. 28toFIG. 30may include not only a plurality of protrusions protruding towards one side of the first conductive-type semiconductor layer111but also a plurality of protrusions protruding towards the other side thereof.

Accordingly, a second contact region R2partially surrounded by the mesa M can be increased. That is, it is possible to secure the second contact region R2disposed between the pluralities of protrusions protruding towards the one side of the first conductive-type semiconductor layer111and the other sides thereof. With this structure, not only in a region near the one side of the first conductive-type semiconductor layer111but also in a region near the other side thereof, efficient current movement can be achieved between the second electrode120on the protrusions and the first electrode140on the second contact region R2. Accordingly, light emission from the region adjacent the other side can be improved.

FIG. 31is an exploded perspective view of an exemplary lighting apparatus to which a light emitting diode in accordance with an embodiment of the disclosed technology is applied.

Referring toFIG. 31, the lighting apparatus according to this embodiment includes a diffusive cover1010, a light emitting diode module1020, and a body1030. The body1030may receive the light emitting diode module1020and the diffusive cover1010may be disposed on the body1030to cover an upper portion of the light emitting diode module1020.

The body1030may have any structure so long as the body can receive and support the light emitting diode module1020to supply electric power to the light emitting diode module1020. For example, the body1030may include a body case1031, a power supply1033, a power source case1035, and a power connector1037, as shown inFIG. 31.

The power supply1033is received in the power source case1035to be electrically connected to the light emitting diode module1020and may include at least one integrated circuit (IC) chip. The IC chip can regulate, change or control characteristics of power supplied to the light emitting diode module1020. The power source case1035may receive and support the power supply1033, and may be disposed inside the body case1031, with the power supply1033secured inside the power source case1035. The power connector115is provided to a lower end of the power source case1035and is coupled to the power source case1035. With this structure, the power connector115is electrically connected to the power supply1033inside the power source case1035and may act as a passage through which external power can be supplied to the power supply1033.

The light emitting diode module1020includes a substrate1023and a light emitting diode1021disposed on the substrate1023. The light emitting diode module1020may be disposed at an upper portion of the body case1031and electrically connected to the power supply1033.

The substrate1023may be selected from any substrate so long as the substrate can support the light emitting diode1021, and may be or include, for example, a printed circuit board including interconnections. The substrate1023may have a shape corresponding to a securing portion at the upper portion of the body case so as to be stably secured to the body case1031. The light emitting diode1021may include at least one of the light emitting diodes according to the above embodiments.

The diffusive cover1010is disposed above the light emitting diode1021and is secured to the body case1031to cover the light emitting diode1021. The diffusive cover1010may be formed of or include a light transmitting material and light orientation characteristics of the lighting apparatus can be regulated through adjustment of the shape and light transmittance of the diffusive cover1010. Accordingly, the diffusive cover1010may be modified in various ways depending upon purposes and applications of the lighting apparatus.

FIG. 32is a sectional view of an exemplary display to which a light emitting diode in accordance with an embodiment of the disclosed technology is applied.

The display according to this embodiment includes a display panel2110, a backlight unit BLU1supplying light to the display panel2110, and a panel guide2100supporting a lower edge of the display panel2110.

The display panel2110may be, for example, a liquid crystal display panel including a liquid crystal layer, without being limited thereto. The display panel2110may be provided at an edge thereof with gate drive PCBs for supplying drive signals to a gate line. In some implementations, the gate drive PCBs2112and2113may be formed on a thin film transistor substrate instead of a separate PCB.

The backlight unit BLU1includes a light source module including at least one substrate2150and a plurality of light emitting diodes2160. The backlight unit BLU1may further include a bottom cover2180, a diffusive sheet2170, a diffusive plate2131, and optical sheets2130.

The bottom cover2180is open at an upper side thereof and may receive the substrate2150, the light emitting diodes2160, the diffusive sheet2170, the diffusive plate2131and the optical sheets2130. In addition, the bottom cover2180may be coupled to the panel guide2100. The substrate2150may be disposed at a lower side of the diffusive sheet2170to be surrounded by the diffusive sheet2170. Alternatively, in the structure wherein a surface of the substrate2150is coated with a reflective material, the substrate2150may be disposed on the diffusive sheet2170. In some implementations, a plurality of substrates2150may be arranged parallel to each other. However, it should be understood that the disclosed technology is not limited thereto and the substrate2150may be realized by a single substrate.

The light emitting diodes2160may include at least one of the light emitting diodes according to the embodiments described above. The light emitting diodes2160may be regularly arranged in a predetermined pattern on the substrate2150. Furthermore, a lens2210is disposed on each of the light emitting diodes2160, thereby improving uniformity of light emitted from the plurality of light emitting diodes2160.

The diffusive plate2131and the optical sheets2130are disposed above the light emitting diodes2160. Light emitted from the light emitting diodes2160may be supplied in the form of surface light to the display panel2110through the diffusive plate2131and the optical sheets2130.

As such, the light emitting diodes according to the embodiments of the disclosed technology may be applied to a direct type display as in this embodiment.

FIG. 33is a sectional view of an exemplary display to which a light emitting diode in accordance with an embodiment of the disclosed technology is applied.

A display according to this embodiment includes a display panel3210on which an image is displayed, and a backlight unit BLU2disposed at the backside of the display panel3210and supplying light. The display includes a frame240supporting the display panel3210and receiving the backlight unit BLU2, and covers3240,3280enclosing the display panel3210.

The display panel3210may be, for example, a liquid crystal display panel including a liquid crystal layer, without being limited thereto. The display panel3210may be provided at an edge thereof with gate drive PCBs for supplying drive signals to a gate line. In some implementations, the gate drive PCBs may be formed on a thin film transistor substrate instead of a separate PCB. The display panel3210is secured by the covers3240and3280disposed at upper and lower sides thereof, and the cover3280disposed at the lower side of the display panel may be coupled to the backlight unit BLU2.

The backlight unit BLU2configured to supply light to the display panel3210includes a lower cover3270partially open at an upper side thereof, a light source module disposed at one side within the lower cover3270and a light guide plate3250disposed parallel to the light source module and converting spot light into surface light. The backlight unit BLU2according to this embodiment may further include optical sheets3230disposed above the light guide plate3250to collect and spread light, and a reflective sheet3260disposed below the light guide plate3250to reflect light, which travels in a downward direction of the light guide plate3250, towards the display panel3210.

The light source module includes a substrate3220and a plurality of light emitting diodes3110arranged at constant intervals on one surface of the substrate3220. The substrate3220may be selected from any substrate so long as the substrate can support the light emitting diodes3110and be electrically connected to the light emitting diodes3110, and may be or include, for example, a printed circuit board. The light emitting diodes3110may include at least one of the light emitting diodes according to the embodiments described above. Light emitted from the light source module enters the light guide plate3250to be supplied to the display panel3210through the optical sheets3230. Through the light guide plate3250and the optical sheets3230, spot light emitted from the light emitting diodes3110can be converted into surface light.

As such, the light emitting diodes according to the embodiments of the disclosed technology may be applied to an edge type display as in this embodiment.

FIG. 34is a sectional view of an exemplary headlight to which a light emitting diode in accordance with an embodiment of the disclosed technology is applied.

Referring toFIG. 34, the headlight includes a lamp body4070, a substrate4020, a light emitting diode4010, and a cover lens4050. The headlight may further include a heat dissipation portion4030, a support rack4060, and a connection member4040.

The substrate4020is secured by the support rack4060and disposed above the lamp body4070to be separated therefrom. The substrate4020may be selected from any substrate so long as the substrate can support the light emitting diode4010, and may be or include, for example, a printed circuit board having a conductive pattern. The light emitting diode4010is disposed on the substrate4020and may be supported and secured by the substrate4020. Further, the light emitting diode4010may be electrically connected to an external power source through the conductive pattern of the substrate4020. The light emitting diode4010may include at least one of the light emitting diodes according to the embodiments described above.

The cover lens4050is placed on an optical path along which light emitted from the light emitting diode4010travels. For example, as shown inFIG. 34, the cover lens4050may be separated from the light emitting diode4010by the connection member4040and may be disposed in a direction in which light emitted from the light emitting diode4010will be supplied. By the cover lens4050, a beam angle and/or a color of light emitted from the headlight to the outside can be regulated. On the other hand, the connection member4040secures the cover lens4050to the substrate4020and is disposed to surround the light emitting diode4010so as to act as a light guide providing a light emission path4045. Here, the connection member4040may be formed of a light reflective material or may be coated with the light reflective material. The heat dissipation portion4030may include heat dissipation fins4031and/or a heat dissipation fan4033, and dissipates heat generated during operation of the light emitting diode4010.

As such, the light emitting diodes according to the embodiments of the disclosed technology may be applied to a headlight as in this embodiment, particularly, to a vehicle headlight.

Although various embodiments have been described above, it should be understood that other implementations are also possible. In addition, some features of a certain embodiment may also be applied to other embodiments in the same or similar ways without departing from the spirit and scope of the disclosed technology.