KR101423719B1

KR101423719B1 - Light emitting device and method for fabricating the same

Info

Publication number: KR101423719B1
Application number: KR1020080027495A
Authority: KR
Inventors: 김규범; 이상준; 한창석; 김광중
Original assignee: 서울바이오시스 주식회사
Priority date: 2008-03-25
Filing date: 2008-03-25
Publication date: 2014-08-04
Also published as: KR20090102204A

Abstract

an n-type nitride semiconductor layer; An active layer formed on the n-type nitride semiconductor layer; A superlattice Mg / AlGaN layer formed by alternately repeating growth of Mg and AlGaN on the active layer; And a p-type nitride semiconductor layer formed on the Mg / AlGaN layer of the superlattice structure. Thus, the electrical conductivity and crystallinity of the p-type nitride semiconductor layer can be improved.

Light-emitting diode, p-GaN growth, Mg / AlGaN, superlattice layer

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a light emitting device,

More particularly, the present invention relates to a light emitting device having a superlattice Mg / AlGaN layer between a p-type nitride semiconductor layer and an active layer, and a manufacturing method thereof.

In general, nitride-based semiconductors are widely used in blue / green light emitting diodes or laser diodes as light sources for full color displays, traffic lights, general lighting and optical communication devices. The nitride-based light-emitting device includes an active layer having a multiple quantum well structure located between n-type and p-type nitride semiconductor layers, and generates light by recombination of electrons and holes in the active layer.

These nitride semiconductor layers are mainly grown by using a metal organic chemical vapor deposition method in which a substrate is placed in a reactor and then a source gas using an organic material source of a Group III metal is supplied into the reactor to grow a nitride semiconductor layer on the substrate do.

On the other hand, the p-type nitride semiconductor layer is formed by using p-AlGaN as an electronic blocking layer (EBL) and mainly using Mg as a dopant. At this time, Mg is bonded to hydrogen to deteriorate the crystallinity of the p- And may not contribute to the electrical conductivity of the p-type nitride semiconductor layer. Such a problem due to the doping of Mg leads to an increase in the leakage current of the light emitting element, reverse voltage characteristic deterioration and poor current diffusion, thereby reducing the luminous efficiency and luminance of the light emitting element.

On the other hand, it is necessary to improve the electrical conductivity of the p-type nitride semiconductor layer in order to lower the driving voltage of the gallium nitride semiconductor light emitting device and to improve the output thereof. However, when the doping concentration of Mg is increased, a phenomenon in which the carrier concentration decreases, so-called self-compensation occurs.

Therefore, it is necessary to sufficiently increase the Mg doping concentration to improve the electrical conductivity of the p-type nitride semiconductor layer and to improve the crystallinity of the p-type nitride semiconductor layer.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light emitting device having a p-type nitride semiconductor layer with improved electrical conductivity and / or crystallinity and a method of manufacturing the same.

According to an aspect of the present invention, there is provided a nitride semiconductor light emitting device including: an n-type nitride semiconductor layer; An active layer formed on the n-type nitride semiconductor layer; A superlattice Mg / AlGaN layer formed by alternately repeating growth of Mg and AlGaN on the active layer; And a p-type nitride semiconductor layer formed on the Mg / AlGaN layer of the superlattice structure.

Preferably, the p-type nitride semiconductor layer may be p-GaN.

Preferably, the Mg / AlGaN layer of the superlattice structure may have the same amount of Mg in each pair consisting of alternately repeatedly grown Mg and AlGaN.

Preferably, the Mg / AlGaN layer of the superlattice structure may have a variable amount of Mg in each pair consisting of alternately repeatedly grown Mg and AlGaN.

Preferably, the p-type nitride semiconductor layer may have a rough surface. The roughness of the surface of the p-type nitride semiconductor layer is caused by excessive Mg.

According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming an n-type nitride semiconductor layer on a substrate; Forming an active layer on the n-type nitride semiconductor layer; Alternately growing Mg and AlGaN alternately on the active layer to form a superlattice Mg / AlGaN layer; And forming a p-type nitride semiconductor layer on the Mg / AlGaN layer of the superlattice structure.

Preferably, the p-type nitride semiconductor layer may be p-GaN.

Preferably, the Mg / AlGaN layer forming step of the super lattice structure is performed in a reactor, and source gases including a Ga source gas, an N source gas, and an Al source gas are supplied into the reactor to form AlGaN The supply of the Ga source gas and the Al source gas supplied into the reactor was stopped to stop the growth of the AlGaN layer but the NH ₃ gas was supplied and the Mg source gas and the NH ₃ gas were supplied into the reactor The Mg layer may be grown on the AlGaN layer, the supply of the Mg source gas supplied into the reactor may be stopped, and the growth of the Mg layer may be stopped, but NH ₃ gas may be supplied and the above process may be repeated.

Preferably, the method further comprises the steps of: forming a Mg / AlGaN layer having the superlattice structure; supplying a source gas containing a Ga source gas, an N source gas, and a Mg source gas into the reactor, And growing the doped p-type nitride semiconductor layer.

Preferably, the Mg source gas may be supplied at the same flow rate for each repetition of the above process.

Preferably, the Mg source gas may be supplied at a different flow rate in each iteration of the above process.

According to embodiments of the present invention, by forming a superlattice Mg / AlGaN layer between the p-type nitride semiconductor layer and the active layer, the crystal defect density, such as the dislocation density, is reduced to improve the crystallinity of the p- . Accordingly, it is possible to provide a light emitting device having a low driving voltage and improved luminous efficiency and emission output. In addition, by doping Mg through the Mg / AlGaN layer having a super lattice structure, Mg can be prevented from diffusing and doping can be appropriately performed at a desired place, thereby increasing the luminous efficiency.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

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

1, the light emitting device includes an n-type nitride semiconductor layer 25, an active layer 27, a superlattice Mg / AlGaN layer 28, and a p-type nitride semiconductor layer 29. The light emitting device may include a substrate 21, a buffer layer 23, a transparent electrode layer 31, an n-electrode 33, and a p-electrode 35.

The substrate 21 refers to a wafer for fabricating a nitride based light emitting device and may be mainly sapphire (Al ₂ O ₃ ) or silicon carbide (SiC), but the present invention is not limited thereto, For example, a heterogeneous substrate such as silicon (Si), gallium arsenide (GaAs), spinel, or the like, or a homogeneous substrate such as GaN.

The buffer layer 23 is for reducing lattice mismatching between the substrate 21 and the nitride semiconductor layer when the nitride semiconductor layer is grown on the substrate 21 and may be formed of an InAlGaN series or SiC or ZnO series material.

On the other hand, the n-type nitride semiconductor layer 25 may be formed mainly of GaN, but not limited thereto, and may be formed of an (Al, In, Ga) N series binary to quaternary nitride semiconductor. In addition, the n-type nitride semiconductor layer 25 may be formed as a single layer or multiple layers, and may include a superlattice layer.

The active layer 27 may be formed of a single quantum well structure or a multiple quantum well structure. In the case of a multiple quantum well structure, a quantum barrier layer and a quantum well layer may be alternately formed by repeating at least 2 times and at most 20 times . The composition of the active layer is determined according to the required emission wavelength, and InGaN is suitable as an active layer (quantum well layer) in order to emit visible light of blue or green series. The quantum barrier layer is formed of a nitride having a band gap larger than that of the quantum well layer, and may be formed of, for example, GaN or InGaN.

The superlattice Mg / AlGaN layer 28 has a superlattice structure formed by alternately repeating growth of Mg and AlGaN between the active layer 27 and the p-type nitride semiconductor layer 29. The Mg / AlGaN layer 28 of the superlattice structure can prevent the dislocation from growing to the p-type nitride semiconductor layer 29 grown thereon, thereby increasing the crystallinity of the p-type nitride semiconductor layer 29, And the diffusion of Mg in the AlGaN layer is also hindered, so that it can be appropriately doped to a desired place.

The p-type nitride semiconductor layer 29 may be formed mainly of GaN, but is not limited thereto. The p-type nitride semiconductor layer 29 may be formed of an (Al, In, Ga) N series binary to quaternary nitride semiconductor. The p-type nitride semiconductor layer 29 may be formed using Mg as a dopant.

The transparent electrode layer 31 may be formed on the p-type nitride semiconductor layer 29 and the transparent electrode layer 31 may be formed of a transparent metal layer such as Ni / Au or a conductive oxide such as ITO.

On the other hand, an n-electrode 33 may be formed on the n-type semiconductor layer 25, and a p-electrode may be formed on the transparent electrode layer 31. The n-electrode and the p-electrode may be formed of various metal materials such as Ti / Al.

The buffer layer, the n-type nitride semiconductor layer and the active layer may be formed by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE) . However, at present, metal organic chemical vapor deposition is mainly used. Therefore, a method of forming the p-type nitride semiconductor layer using the metal organic chemical vapor deposition method will be described below.

FIG. 2 is a flowchart illustrating a method of manufacturing a light emitting device according to an embodiment of the present invention. FIG. 3 is a timing diagram illustrating a method of manufacturing a light emitting device according to an exemplary embodiment of the present invention.

Referring to FIG. 2, first, a substrate 21 is prepared (S01). The substrate 21 may have a buffer layer 23, an n-type nitride semiconductor layer 25, and an active layer 27 thereon. Such a substrate 21 may be prepared by loading the substrate 21 in a reactor and supplying source gases into the reactor to deposit the buffer layer 23, the n-type nitride semiconductor layer 25 and the active layer 27.

The buffer layer 23 may be formed of nitride, and the method and materials for forming the buffer layer are well known, and thus the detailed description thereof will be omitted.

The n-type nitride based semiconductor layer 25 may be formed using Si as a dopant, and an inert gas such as SiH ₄ or Si ₂ H ₄ or a metal organic source such as DTBSi may be used as the source of Si have. The Si concentration may be in the range of 1 × 10 ¹⁷ / cm 3 to 5 × 10 ¹⁹ / cm 3, and the n-type nitride semiconductor layer may be formed in a thickness of 1.0 to 5.0 μm.

The active layer 27 has a single quantum well structure, or _{In x Ga1 1-x N (} 0.1 <x <1) quantum well layers and _{In y Ga 1-y N (} 0 <y <0.5) quantum barrier layer is twice And can be formed into a multiple quantum well structure repeated no more than 20 times. Preferably, each quantum well layer may be formed to a thickness of 1 to 5 nm and an In content (0.1 < x < 0.4) and each quantum barrier layer may be formed to a thickness of 5 to 40 nm and an In content .

Referring to FIGS. 2 and 3, a Ga source gas, an N source gas, and an Al source gases are supplied into the reactor to grow an AlGaN layer 28a (S03). The supply of the source gases takes place during the time T1.

As the Ga source, trimethylgallium (TMGa) or triethylgallium (TEGa) can be used. As the N source gas, ammonia (NH ₃ ) or dimethylhydrazine (DMHy) can be used. As the Al source gas, trimethyl aluminum ; can be used _{TMAl, Al (CH 3) 3} ).

The T1 time is set to the time required to form the AlGaN layer 28a of the required thickness.

Thereafter, the supply of the Ga source and Al source gas supplied into the reactor is stopped to stop the growth of the AlGaN layer (S05). The growth interruption occurs during the T2 time.

The reactor is equipped with an exhaust pump to discharge gases in the reactor, so that the Ga source gas and the Al source gas remaining in the reactor are mostly discharged to the outside over time after the supply of the source gases is stopped. The time T2 may be 1 to 60 seconds for discharging the Ga source gas and the Al source gas.

When the growth is stopped at a relatively high temperature, the nitrogen atoms are dissociated from the nitride semiconductor layer grown on the substrate to form nitrogen vacancies. Therefore, NH ₃ gas can be supplied during the growth stop of the nitride semiconductor layer to supply N atoms. In this embodiment, when the N source gas contains NH ₃ , the supply of the Ga source gas and the Al source gas may be stopped and NH ₃ may be continuously supplied. Alternatively, the N source gas can be supplied to the NH ₃ separately in the case that does not contain NH _3, the growth interruption step (S05).

Thereafter, Mg source gas and NH ₃ gas are supplied into the reactor to grow the Mg layer 28b on the AlGaN layer 28a (S07). As the Mg source, CP ₂ Mg can be used.

The Mg growth occurs for T3 hours, and T3 can be in the range of 1 to 60 seconds.

Thereafter, the supply of the Mg source gas supplied into the reactor is stopped to stop the growth of the Mg layer 28b (S09). The growth interruption occurs for T4 hours.

The reactor is equipped with an exhaust pump to discharge the gas in the reactor, so that the Mg source gas remaining in the reactor is discharged to the outside most of the time after the supply of the Mg source gas is stopped. The time T4 may be from 1 to 60 seconds to discharge the Mg source gas.

The growth of the AlGaN layer 28a, the stop of growth, the growth of the Mg layer 28b, and the growth stopping steps described above are repeated several times (S11). At this time, the AlGaN layer 28a and the Mg layer 28b to be grown may have a total stacked thickness of 300-400 Å. The Mg / AlGaN layer 28 of the superlattice structure may form 10 to 100 pairs. Accordingly, the thickness of each of the AlGaN layer 28a and the Mg layer 28b in the superlattice structure can be determined to have a thickness for realizing the total thickness.

The n-type nitride semiconductor layer 25, the active layer 27, the superlattice Mg / AlGaN layer 28, and the p-type nitride semiconductor layer 29 are grown in the same reactor by using MOCVD, Can be grown.

The Ga source gas, the N source gas, and the Mg source gas are supplied into the reactor again to grow the Mg-doped p-type nitride semiconductor layer 29 (S13).

Thereafter, the p-type nitride semiconductor layer 29 and the active layer 27 formed on the substrate 21 are patterned to form the transparent electrode layer 31, the n-electrode 33 and the p-electrode 35 The light emitting element of Fig. 1 is completed.

The Mg / AlGaN layer 28 of superlattice structure in which the AlGaN layer 28a and the Mg layer 28b are alternately stacked is formed between the p-type nitride semiconductor layer 29 and the active layer 27, It is possible to increase the crystallinity of the p-type nitride semiconductor layer 29, to increase the hole concentration, to prevent diffusion of Mg in the AlGaN layer, Where appropriate.

In Experiment 1, the light emission effect of Mg / AlGaN layer with superlattice structure was measured by changing the amount of Mg.

- Mg: temperature 980 캜, time 0.5 min, Mg 240 sccm, 360 sccm, 480 sccm

- AlGaN: on 980 캜, time 0.5 min, TMGa 13 sccm, Al 40/82/31

- 12 pairs of Mg / AlGaN layers

FIG. 4 is a graph showing the amount of light emission according to the amount of Mg, FIG. 5 is a photograph of the surface of p-GaN grown at 240 sccm of Mg, and FIG. 6 is a photograph of the surface of p-GaN grown at 360 sccm of Mg. In the case of Mg 480 sccm, it was impossible to measure by surface defects.

As can be seen from FIG. 4, when the Mg / AlGaN layer of the superlattice structure was grown, the amount of light emission was increased by increasing the amount of Mg. 5 and 6, it was confirmed that the surface of the p-GaN grown on the Mg / AlGaN layer was roughened by increasing the amount of Mg in the growth of the superlattice Mg / AlGaN layer .

As can be seen from the above experimental results, when the amount of Mg is increased during the growth of the Mg / AlGaN layer, the surface of the p-GaN grown on the Mg / AlGaN layer becomes rough due to excessive Mg, ), As shown in FIG. Here, p-loughening means lubrication of the surface of the p-type semiconductor layer to improve the light emission effect.

The method of forming the p-type nitride semiconductor layer in this embodiment can be used for manufacturing not only light emitting diodes but also other nitride based optical devices, for example, laser diodes.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, the invention is not to be limited to the details of the embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. In addition, those skilled in the art will appreciate that many modifications and variations are possible without departing from the scope of the present invention.

For example, in the description of the Mg / AlGaN layer of the superlattice structure in the embodiments, the AlGaN layer is grown first and then the Mg layer is grown. However, the present invention is not limited to this, A process of growing the AlGaN layer may be performed.

In addition, in the present embodiments, when Mg and AlGaN are stacked alternately to form Mg / AlGaN layers having superlattice structure composed of several pairs, the amount of Mg is kept constant for each pair. However, , But it is also possible to change the amount of Mg such that the amount of Mg is gradually decreased or increased for each pair of Mg / AlGaN layers, for example.

In addition, although the present embodiment is limited to T1 to T4 in the detailed description of FIG. 3, it can be modified as necessary without departing from the scope of the present invention.

2 is a flowchart illustrating a method of manufacturing a light emitting device according to an embodiment of the present invention

3 is a timing diagram for explaining a method of manufacturing a light emitting device according to an embodiment of the present invention.

4 is a graph illustrating the amount of light emission according to the amount of Mg according to an embodiment of the present invention.

5 is a photograph of a surface of p-GaN grown at a Mg concentration of 240 sccm according to an embodiment of the present invention.

6 is a photograph of a surface of p-GaN grown at 360 sccm of Mg according to an embodiment of the present invention.

Claims

an n-type nitride semiconductor layer;

An active layer formed on the n-type nitride semiconductor layer;

A superlattice Mg / AlGaN layer formed by alternately repeating growth of Mg and AlGaN on the active layer;

And a p-type nitride semiconductor layer formed on the Mg / AlGaN layer of the superlattice structure,

The superlattice Mg /

Wherein the amount of Mg is variable for each pair consisting of the alternately repeatedly grown Mg and AlGaN.

The method according to claim 1,

And the p-type nitride semiconductor layer is p-GaN.

delete

The method according to claim 1,

Wherein the p-type nitride semiconductor layer has a rough surface.

Forming an n-type nitride semiconductor layer on the substrate;

Forming an active layer on the n-type nitride semiconductor layer;

Alternately growing Mg and AlGaN alternately on the active layer to form a superlattice Mg / AlGaN layer;

And forming a p-type nitride semiconductor layer on the Mg / AlGaN layer of the superlattice structure,

In the Mg / AlGaN layer forming step of the super lattice structure,

Lt; RTI ID = 0.0 >

Source gases including a Ga source gas, an N source gas, and an Al source gas are supplied into the reactor to grow an AlGaN layer on the active layer,

The supply of the Ga source gas and the Al source gas supplied into the reactor is stopped to stop the growth of the AlGaN layer and NH ₃ gas is supplied,

An Mg source gas and an NH ₃ gas are supplied into the reactor to grow an Mg layer on the AlGaN layer,

A step of stopping the supply of the Mg source gas supplied into the reactor to stop the growth of the Mg layer, and supplying an NH ₃ gas to form a Mg / AlGaN layer;

And repeating the process of forming the Mg / AlGaN layer,

Wherein the Mg source gas is supplied at a different flow rate each time the Mg / AlGaN layer is formed.

The method of claim 6,

And the p-type nitride semiconductor layer is p-GaN.

delete

The method of claim 6,

The step of forming the p-type nitride semiconductor layer on the Mg / AlGaN layer of the superlattice structure includes:

And supplying source gases including a Ga source gas, an N source gas, and an Mg source gas into the reactor to grow the Mg-doped p-type nitride semiconductor layer on the substrate.

delete