KR101635609B1 - Light emitting diode and method of fabricating the same - Google Patents

Abstract

A light emitting diode and a method for manufacturing the same are disclosed. The light emitting diode includes an electronic block layer positioned between the active layer and the p-type semiconductor layer. The electronic block layer includes a first block region having a wider band gap than the active layer, a second block region having a band gap larger than that of the active layer, And a third block region located between the second block region and the p-type semiconductor layer. Here, the second block region includes the p-type impurity at a higher concentration than the third block region, and the third block region includes the p-type impurity at a higher concentration than the first block region. Accordingly, it is possible to improve the hole injection efficiency while preventing the electron overflow.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a light emitting diode (LED)

The present invention relates to a light emitting diode and a method of manufacturing the same, and more particularly, to a light emitting diode employing an electronic block layer and a method of manufacturing the same.

In general, AlInGaN-based nitride has excellent thermal stability and has a direct bandgap energy band structure, and thus has attracted much attention as a material for light emitting diodes in the blue and ultraviolet region.

A light emitting diode using a gallium nitride semiconductor generally includes an N-type GaN layer, an active layer, and a P-type GaN layer, and an N-type electrode and a P-type electrode are connected to the N-type GaN layer and the P- When a predetermined current is applied to the N-type electrode and the P-type electrode of the light emitting device, electrons injected from the N-type GaN layer and holes injected from the P-type GaN layer are recombined in the active layer to correspond to the band gap of the active layer, Thereby emitting light of energy.

On the other hand, since the mobility of electrons is considerably larger than the mobility of holes, the electrons in the active layer can be introduced into the p-type GaN layer before they are bonded to the holes. In order to prevent such electrons from overflowing, an electron blocking layer (EBL) is generally formed between the active layer and the P-type GaN layer (see patent literature). The electron blocking layer has a higher bandgap than that of the active layer, so electrons can be trapped in the active layer to increase the recombination rate of electrons and holes.

However, an electronic block layer such as an AlGaN layer not only provides an energy barrier for electrons, but also forms an energy barrier for holes. As a result, the injection efficiency of holes is decreased and the recombination rate is reduced.

Korean Patent Laid-Open Publication No. 10-2010-0003331 discloses a technique in which an electronic block layer is divided into a first block layer and a second block layer in order to improve the injection efficiency of holes and a second block layer is formed into a composition gradient layer . According to this, the formation of the second block layer as a composition gradient layer can help the hole injection from the p-type GaN layer into the active layer.

However, even when the composition gradient layer is adopted, since the p-type AlGaN layer has a wider band gap than the GaN layer, it can still function as an energy barrier against holes. In order to prevent this, the p-type AlGaN layer (first block layer) needs to be doped at a high concentration. However, when the AlGaN layer is doped at a high concentration, the crystallinity of the AlGaN layer is deteriorated and the leakage current can be increased. Furthermore, doped Mg may precipitate as a metal rather than act as an acceptor and may not contribute to increasing the carrier concentration. Furthermore, when the first block layer is doped at a high concentration, Mg may diffuse into the active layer, which may deteriorate the optical characteristics of the active layer.

Korean Patent Publication No. 10-2010-0003331

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light emitting diode having improved hole injection efficiency while preventing electron overflow and a method of manufacturing the same.

Another object of the present invention is to provide a light emitting diode having a high crystalline p-type impurity doping concentration and a good crystalline electronic block layer without deteriorating the characteristics of the active layer.

A further object of the present invention is to provide a method of manufacturing a light emitting diode capable of doping a p-type impurity into an electronic block layer at a high concentration while maintaining the crystal quality.

A light emitting diode according to one aspect of the present invention includes an n-type semiconductor layer, a p-type semiconductor layer, an active layer positioned between the n-type semiconductor layer and the p-type semiconductor layer, and an active layer located between the active layer and the p- Lt; / RTI > The electronic block layer may include a first block region located between the active layer and the p-type semiconductor layer and having a wider bandgap than the active layer, a second block region located between the first block region and the p- And a third block region located between the second block region and the p-type semiconductor layer. Here, the second block region includes a p-type impurity with a higher concentration than the third block region, and the third block region includes a p-type impurity with a higher concentration than the first block region.

It is possible to provide a light emitting diode having improved hole injection efficiency while preventing electron overflow by disposing a second block region having a relatively high concentration between the first block region and the third block region. In addition, by forming the second block region at a relatively high concentration, it is possible to provide a light emitting diode having a good crystalline electronic block layer without deteriorating the characteristics of the active layer.

In some embodiments, the first block region, the second block region, and the third block region may be AlInGaN-based semiconductor layers of the same composition ratio. Therefore, the electron blocking layer can be formed by doping only the doping concentration of the p-type impurity, for example, Mg, differently in the regions of the AlInGaN-based semiconductor layer having the same composition ratio, so that the manufacturing process can be simplified.

In other embodiments, the first block region, the second block region, and the third block region are AlInGaN-based semiconductor layers, and the second block region has a different composition ratio from the first block region and the third block region Lt; / RTI > The second block region may have a band gap narrower than the first and third block regions. Furthermore, the first block region and the third block region have a wider bandgap than the p-type semiconductor layer. The p-type semiconductor layer may include a p-type GaN layer.

Since the second block region has a narrower bandgap than the first and third block regions, holes can be easily supplied from the p-type semiconductor layer to the electronic block layer.

Meanwhile, the second block region may have a relatively small thickness as compared with the first block region, and the first block region may have a relatively small thickness as compared with the third block region. The second block region may have a thickness within a range of 10 to 100 angstroms.

Since the second block region is formed relatively thin, the crystallinity of the second block region can be prevented from being deteriorated even when the p-type impurity is doped at a high concentration, and thus the crystalline quality of the entire electronic block layer can be satisfactorily maintained.

In addition, by forming the first block region to be relatively thinner than the third block region, it is possible to improve the injection efficiency of holes injected into the active layer.

Meanwhile, the first block region may be in contact with the active layer, and both side surfaces of the second block region may be in contact with the first block region and the third block region, respectively.

Furthermore, the third block region may be a compositionally graded layer. That is, it may be a composition gradient layer whose band gap decreases from the second block region side toward the p-type semiconductor layer side. Hence, holes can be easily supplied from the p-type semiconductor layer into the electron block layer.

The light emitting diode may further include a first electrode contacting the n-type semiconductor layer, and a second electrode contacting the p-type semiconductor layer.

According to another aspect of the present invention, there is provided a method of fabricating a light emitting diode, comprising: forming an n-type semiconductor layer on a substrate; forming an active layer on the n-type semiconductor layer; forming a first block region, And a third block region, and forming a p-type semiconductor layer on the electronic block layer. Here, the second block region is formed by doping the p-type impurity at a higher concentration than the first block region and the third block region.

The p-type impurity in the second block region can be diffused into the first block region and the third block region by doping the second block region located between the first block region and the third block region with a high concentration. Thus, an electronic block layer having a high concentration of p-type impurity can be produced.

The first block region may be formed without intentionally doping, and the third block region may be formed by doping a p-type impurity. Since the first block region is not intentionally doped, the p-type impurity in the electronic block layer can be prevented from diffusing into the active layer.

The p-type impurity may be Mg, and the second block region may be formed by supplying a flow rate of a p-type impurity source of 2 to 5 times the p-type impurity source flow rate at the time of forming the third block region have. The p-type impurity source may be Cp2Mg.

In addition, the first to third block regions may be formed of AlInGaN-based semiconductor layers, and the respective block regions may be formed of semiconductor layers having the same composition ratio or different composition ratios.

The second block region may be relatively thinner than the first block region, and the first block region may be formed to be relatively thinner than the third block region.

According to the embodiments of the present invention, it is possible to provide an electron blocking layer having a p-type impurity at a higher concentration than in the prior art, thereby improving electron injection efficiency while preventing electron overflow. In addition, by forming the second block region at a relatively high concentration, it is possible to provide a light emitting diode having a good crystalline electronic block layer without deteriorating the characteristics of the active layer.

1 is a cross-sectional view illustrating a light emitting diode according to an embodiment of the present invention.
2 is a schematic cross-sectional view for explaining diffusion of a p-type impurity in an electron blocking layer.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, etc. of constituent elements can be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

1 is a cross-sectional view illustrating a light emitting diode according to an embodiment of the present invention.

1, the light emitting diode includes an n-type semiconductor layer 30, an active layer 40, an electron blocking layer 50, and a p-type semiconductor layer 60. The electronic block layer 50 includes a first block region 51, a second block region 52, and a third block region 53. The light emitting diode may include a substrate 10 and a buffer layer 20 and may include a transparent electrode 70, an n-electrode 80, and a p-electrode 90.

The substrate 10 may be a sapphire substrate, a SiC substrate, a Si substrate, a spinel substrate, or a GaN substrate. The substrate 10 may be a patterned sapphire substrate (PSS).

The buffer layer 20 may be formed of undoped GaN, for example, as a layer for mitigating the occurrence of defects such as dislocation between the substrate 10 and the n-type semiconductor layer 30. A nucleus layer (not shown) may be formed between the buffer layer 20 and the substrate 10, and the nucleus layer may be formed of (Al, Ga) N at a low temperature of 400 to 600 ° C. The core layer may be formed to a thickness of about 25 nm. After the nucleation layer is formed on the substrate 10, the buffer layer 20 is formed at a relatively high temperature.

The n-type semiconductor layer 30 is formed on the buffer layer 20 by a gallium nitride-based semiconductor layer doped with an n-type impurity, for example, Si. The n-type semiconductor layer 30 may be formed as a single layer as shown in the figure, but not limited thereto. The n-type semiconductor layer 30 may include an n-type GaN layer, and the n-type electrode 80 may contact the n-type GaN layer.

The active layer 40 may have a single quantum well structure or a multiple quantum well structure in which barrier layers and quantum well layers are alternately stacked. The active layer 40 is formed on the n-type semiconductor layer 30. The barrier layer may be formed of a gallium nitride-based semiconductor layer having a larger bandgap than the quantum well layer, for example, GaN, InGaN, AlGaN, or AlInGaN. The quantum well layer may be formed of InGaN, and the In composition ratio in the InGaN quantum well layer is determined by the desired light wavelength. The barrier layer and the quantum well layer of the active layer 40 may be formed of undoped undoped layers to improve the crystallinity, but impurities may be doped in some or all of the active regions to lower the forward voltage.

An electron blocking layer 50 is formed on the active layer 40. The electronic block layer 50 includes a first block region 51, a second block region 52, and a third block region 53. The first block region 51 can be in contact with the active layer 40. The first block region 51 has a wider bandgap than the active layer 40, particularly the barrier layer. The second block region 52 is located between the first block region 51 and the third block region 53 and has a relatively high p-type impurity concentration compared to the first and third block regions 51 and 53 Such as Mg.

The first, second and third block regions 51, 52 and 53 may be formed of an AlInGaN-based semiconductor layer, for example, AlGaN. These regions 51, 52, and 53 may be formed of AlInGaN-based semiconductor layers having the same composition ratio, but not limited thereto, and AlInGaN-based semiconductor layers having different composition ratios. For example, the second block region 52 may be formed of a semiconductor layer having a band gap narrower than that of the first and third block regions 51 and 53. The third block region 53 may be formed of a semiconductor layer having a bandgap equal to or narrower than that of the first block region 51. [ In some embodiments, the third block region 53 may be formed of a compositionally graded layer in which the band gap is narrowed toward the p-type semiconductor layer 60 in the second block region 52.

The second block region 52 may have a relatively thin thickness as compared with the first and third block regions 51 and 53. The first block region 51 may have a thickness smaller than that of the third block region 53, It is possible to have a relatively thin thickness. The second block region 52 may have a thickness within a range of 10 to 100 angstroms, for example. In addition, the thickness of each of the block regions 51, 52 and 53 can be adjusted in relation to the band gap width of each region. That is, the larger the band gap is, the smaller the thickness can be formed.

The first block region 51 may be formed without intentionally doping and the second block region 52 and the third block region 53 may be formed by doping p-type impurities such as Mg. Here, the second block region 52 may be formed at a high concentration by forming a flow rate of 2 to 5 times the flow rate of the p-type impurity source when the third block region 53 is formed.

Taking the case of using Cp2Mg as the p-type impurity source, TMGa, TMAl and NH3 are first fed into the chamber to form an AlGaN semiconductor layer (first block region 51). Subsequently, Cp2Mg is supplied while maintaining the flow rates of the TMGa, TMAl, and NH3, thereby forming a highly doped AlGaN semiconductor layer (second block region 52). Thereafter, the flow rate of Cp2Mg is decreased while maintaining the flow rate of the other source, thereby forming a relatively low-concentration AlGaN semiconductor layer (third block region 53). The third block region 53 may be formed by supplying Cp2Mg at a flow rate of 0.5 umol / min to 2.0 umol / min, for example, and the second block region 52 may be formed by supplying Cp2Mg at a flow rate of 0.5 umol / And supplying Cp2Mg at a flow rate of 2 to 5 times.

In this case, the p-type impurity 55 doped at a high concentration in the second block region 52 is diffused into the first block region 51 and the third block region 53, as shown in Fig. Therefore, although the first block region 51 is not intentionally doped, the p-type impurity diffused in the second block region 53 remains at a low concentration. In addition, the third block region 53 contains the p-type impurity at a higher concentration than the actual doping concentration, and the second block region 52 contains the p-type impurity at a lower concentration than the actual doping concentration do.

The first, second and third block regions 51, 52 and 53 are formed of AlGaN having the same composition ratio. However, the first block region 51, the second block region 52, During the formation of the region 53, the flow rates of TMGa, TMAl, and NH3 may be changed to form block regions having different composition ratios, or TMIn may be further supplied.

In the present invention, since the thickness of the second block region 52 is relatively thin, the crystallinity does not deteriorate even if the second block region 52 is heavily doped. Further, since the p-type impurity doped in the second block region 52 is diffused into the first and third block regions 51 and 53, p-type impurities such as Mg precipitate in the second block region 52 Can be prevented. In addition, by forming the first block region 51 without intentionally doping, it is possible to prevent or alleviate the diffusion of the p-type impurity into the active layer 40, so that the crystalline and optical characteristics of the active layer 40 can be maintained.

The p-type semiconductor layer 60 is formed on the electron blocking layer 50. [ The p-type semiconductor layer 60 may be formed as a single layer, but is not limited thereto and may be formed of multiple layers. The p-type semiconductor layer 60 may include a p-type GaN layer, and the first block region 51 and the third block region 53 may have a wider band gap than the p-type GaN layer have.

On the other hand, the first electrode 80, that is, the n-electrode is in contact with the n-type semiconductor layer 30, and the second electrode is in contact with the p-type semiconductor layer 60. The second electrode may include a transparent electrode 70 and a p-electrode 90.

The semiconductor layers 20 to 60 may be grown on the substrate 10 using a metalorganic chemical vapor deposition method and the p-type semiconductor layer 60, the electron blocking layer 50, and the active layer 40 A part of the n-type semiconductor layer 30 can be exposed by patterning. Thereafter, the n-electrode 80 may be formed on the exposed n-type semiconductor layer 30.

Although the horizontal type light emitting diode has been described here, the present invention is not limited to the light emitting diode having the specific structure, and can be applied to the vertical type light emitting diode or the flip chip type light emitting diode.

10: substrate, 20: buffer layer, 30: n-type semiconductor layer, 40: active layer, 50:
51: first block area, 52: second block area, 53: third block area
60: p-type semiconductor layer, 70: transparent electrode, 80: n-electrode, 90: p-

Claims (15)

an n-type semiconductor layer;
a p-type semiconductor layer;
An active layer located between the n-type semiconductor layer and the p-type semiconductor layer; And
And an electron blocking layer positioned between the active layer and the p-type semiconductor layer,
Wherein the electronic block layer comprises:
A first block region located between the active layer and the p-type semiconductor layer and having a band gap wider than the active layer;
A second block region located between the first block region and the p-type semiconductor layer; And
And a third block region located between the second block region and the p-type semiconductor layer,
Wherein the second block region includes a p-type impurity having a higher concentration than the third block region,
And the third block region includes a p-type impurity with a higher concentration than the first block region. The method according to claim 1,
Wherein the first block region, the second block region, and the third block region are AlInGaN-based semiconductor layers of the same composition ratio. The method according to claim 1,
The first block region, the second block region, and the third block region are AlInGaN-based semiconductor layers,
Wherein the second block region has a composition ratio different from that of the first block region and the third block region,
And the second block region has a narrower bandgap than the first and third block regions. The method of claim 3,
Wherein the first block region and the third block region have a wider bandgap than the p-type semiconductor layer. The method of claim 4,
Wherein the p-type semiconductor layer comprises a p-type GaN layer. The method according to claim 1,
Wherein the second block region has a thickness smaller than that of the first block region,
Wherein the first block region has a relatively smaller thickness than the third block region. The method of claim 6,
And the second block region has a thickness within a range of 10 to 100 angstroms. The method of claim 6,
The first block region is in contact with the active layer,
And both side surfaces of the second block region are in contact with the first block region and the third block region, respectively. The method according to claim 1,
The third block region is a composition gradient layer formed of an AlInGaN-based semiconductor layer and having a band gap decreasing from the second block region side toward the p-type semiconductor layer side. The method according to claim 1,
A first electrode contacting the n-type semiconductor layer; And
And a second electrode contacting the p-type semiconductor layer. An n-type semiconductor layer is formed on a substrate,
An active layer is formed on the n-type semiconductor layer,
Forming an electronic block layer including a first block region, a second block region and a third block region on the active layer,
And forming a p-type semiconductor layer on the electronic block layer,
The second block region is formed by doping a p-type impurity at a higher concentration than the first block region and the third block region,
The first block region is formed without intentional doping,
And the third block region is formed by doping a p-type impurity. An n-type semiconductor layer is formed on a substrate,
An active layer is formed on the n-type semiconductor layer,
Forming an electronic block layer including a first block region, a second block region and a third block region on the active layer,
And forming a p-type semiconductor layer on the electronic block layer,
The second block region is formed by doping a p-type impurity at a higher concentration than the first block region and the third block region,
The p-type impurity is Mg,
And the second block region is formed by supplying a flow rate of a p-type impurity source of 2 to 5 times the flow rate of the p-type impurity source at the time of forming the third block region. The method according to claim 11 or 12,
Wherein the first to third block regions are formed of AlInGaN-based semiconductor layers. The method according to claim 11 or 12,
The second block region is formed to be relatively thin compared to the first block region,
Wherein the first block region is relatively thinner than the third block region. delete

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