JPH07249820A - Semiconductor light-emitting element - Google Patents

Abstract

PURPOSE:To form a high-efficiency light-emitting center inside a light-emitting layer at high density and to realize a high-brightness and short-wavelength light-emitting operation by a method wherein the light-emitting layer which uses a GaN-based mate rial and whose composition is specific is doped with a specific element. CONSTITUTION:In a semiconductor light-emitting element, a double heterojunction structure in which a light-emitting layer 14 composed of GaxAlyIn1-x-yN (where 0<=x<=1 and 0<=y<1) is sandwiched between, and held by, a first-conductivity-type clad layer 13 and a second-conductivity-type clad layer 15 is formed on a substrate 11. In the semiconductor light-emitting element, the light-emitting layer 14 is doped with at least one kind of element selected from a group composed of P, As, Sb and B, and an isoelectronic trap which is formed of the doped element is used as the light-emitting center. Thereby, when N atoms in GaN are replaced by As atoms, holes are restrained in a narrow range at about an atomic distance due to the large difference in an electron affinity between the N atoms and the As atoms, the overlap of the wave function of electrons and the holes is small even at a high concentration, and a drop in light- emitting efficiency is suppressed. As a result, the high brightness of the semiconductor light-emitting element can be achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device using a compound semiconductor material, and more particularly to a semiconductor light emitting device using a GaN material.

[0002]

2. Description of the Related Art GaN, which is one of III-V group compound semiconductors containing nitrogen, has a large band gap of 3.4 eV and is a direct transition type, and is expected as a material for a short wavelength blue light emitting device. . In a semiconductor light emitting device using a GaN-based material, the light emitting layer is usually a p-type layer to which a group II acceptor impurity such as Zn or Mg is added, and light emission from a deep level (light emission center) created by the impurity is used. is doing.

In this type of semiconductor light emitting device, it is necessary to increase the number of light emitting centers in the light emitting layer in order to suppress the brightness saturation and achieve high brightness. To increase the light emitting centers, however, the light emitting layer is required. When impurities are added at a high concentration, the wavefunctions of the electrons bound to the acceptors overlap with each other and the luminous efficiency sharply decreases. Furthermore, when light emission due to a transition with a donor impurity is used, relatively high concentration doping is possible, but this is low in efficiency because the light emission involves spatial movement of electrons.

These problems become particularly serious when trying to realize a green-blue semiconductor laser, and an operation example of a semiconductor laser using a GaN-based material has not been reported so far.

[0005]

As described above, the conventional Ga
In a semiconductor light emitting device using an N-based material, when impurities are added to the light emitting layer at a high concentration in order to increase the light emitting center, the wave functions of electrons bound to the acceptors are overlapped with each other, resulting in a sharp decrease in light emitting efficiency. Further, even if the light emission due to the transition with the donor impurity is used, there is a problem that the light emission is accompanied by the spatial movement of electrons and thus the light emission efficiency is low.

The present invention has been made in consideration of the above circumstances, and it is an object of the present invention to form a highly efficient light emitting center in a light emitting layer using a GaN-based material at a high density. An object of the present invention is to provide a semiconductor light emitting device that can realize luminance short wavelength light emission.

[0007]

In order to solve the above problems, the present invention employs the following configurations. That is, the present invention has, on a _{substrate, Ga x Al y In 1-} xy N (0 <x ≦
In a semiconductor light emitting device having a double heterojunction structure in which a light emitting layer of 1,0 ≦ y <1) is sandwiched between first-conductivity-type and second-conductivity-type cladding layers, P,
At least one selected from the group consisting of As, Sb, Bi, and B is added, and an electron trap formed by the added element is used as an emission center.

Here, the following are preferred embodiments of the present invention. (1) on a _{substrate, Ga s Al t In 1-} st N layer (0 <s ≦
1, 0 <t ≦ 1) first conductivity type clad layer, G
_{a x Al y In 1-xy} N layer (0 <x ≦ 1,0 ≦ y <1,
y <t) light emitting layer and Ga _s Al _t In _1-st N
In a semiconductor light emitting device having a double heterojunction structure composed of a second conductivity type cladding layer made of, P, As, Sb, Bi or B is added to the light emitting layer, and the added element is formed. The luminescence center is the isoelectronic trap. (2) Use a sapphire substrate or a SiC substrate as the substrate. (3) The n-type cladding layer is Si-doped GaN, the p-type cladding layer is Mg-doped GaN, and the light-emitting layer is As-doped Ga.
Be N. (4) The p-type and n-type cladding layers are GaAlN, and the light emitting layer is GaN. (5) The p-type and n-type clad layers are InGaAlN, and the light emitting layer is InGaN. (6) P, As, Sb, Bi or B added to the light emitting layer
The concentration of 1 × 10 ^{18 to} 5 × 10 ¹⁹ cm ⁻³ .

[0009]

The effect of decreasing the luminous efficiency when adding a high concentration of 1 × 10 ¹⁸ cm ⁻³ or more to the light emitting layer (active layer) is the greatest reason for the decrease in the light emitting efficiency. This is because the energy is dissipated due to the overlapping of two, and in order to prevent this, it is convenient that the spread of the wave function in the bound state is small.

According to the research conducted by the present inventors, N in GaN is
By replacing the atoms with P, As, Sb, and Bi having the same valence, holes are bound to an extremely narrow range of the interatomic distance due to the large difference in electron affinity between the N atom and these atoms. Therefore, it was found that even at a high concentration, the wavefunctions of electrons and holes do not overlap each other, and the decrease in light emission efficiency is dramatically suppressed. Such a phenomenon is caused by GaN
The same can be expected for not only GaInN, GaAlN, and AlGaInN.

Therefore, as in the present invention, P, A is formed in the light emitting layer.
If s, Sb and Bi are added and an electron trap formed by these atoms is used as a light emission center, a highly efficient light emission center can be formed at a high density, which is particularly effective when a double heterojunction is formed. This is because, in the double heterojunction, holes and electrons are injected at a higher concentration than in the homojunction, so that it is necessary to form a light emitting center with a higher concentration.

Further, according to this method, not only the brightness saturation can be suppressed but also the luminous efficiency is greatly improved because the third particles which interact with each other by the Coulomb force do not exist. The emission wavelength becomes longer as the atomic number and concentration of the impurity atom substituting the N atom increase. Furthermore, GaInN, GaA
By adding it to a mixed crystal of 1N, AlGaInN, etc.,
The emission wavelength can be further changed.

However, even in this method, the luminous efficiency decreases at a high concentration where the amount of impurities added exceeds 1 × 10 ²⁰ cm ^-3. Therefore, in order to make this method more effective, the concentration of the luminescent centers in the luminescent layer should be improved. Is 1 × 10 ¹⁸ cm ^-3 or more 5 × 10 ¹⁹ cm ^-3
The following is desirable. Another atom that acts in this way is B. In this case, the B atom substituted with the Ga atom binds the electron and acts as an emission center. As described above, according to the present invention, it is possible to significantly increase the brightness of a semiconductor light emitting device using a III-V group compound semiconductor containing nitrogen such as GaN.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a sectional view showing an element structure of a blue LED according to a first embodiment of the present invention. Here, an n-type GaN cladding layer 13 (Si-doped: 5 × 10 ¹⁷ cm ⁻³ , thickness 1 μm), a thickness of As doped, on a sapphire substrate 11 with a GaN buffer layer 12 having a thickness of 50 nm interposed therebetween. 0.5 μm GaN light-emitting layer 14, p-type GaN cladding layer 15 (Mg-doped: 1 × 10 ¹⁸ cm ⁻³ , thickness 1)
μm) are sequentially stacked to form a double heterojunction structure. Then, the p-side electrode 16 is formed on a part of the clad layer 15, and the n-side electrode 1 is formed on the side surface of the buffer layer 12.
7 are formed.

The concentration of As in the light emitting layer 14 is 5 × 10 ¹⁹ c
m ^-3 . As the emission center, in addition to As, P, Sb,
Bi, B and the like can be used, but P or As is superior for blue because of the ease of crystal growth and the solubility. B
Can be added at a higher concentration.

With such a structure, by adding As to GaN which is the light emitting layer 14, the N atom in GaN is replaced with As having the same valence as the N atom and the As atom. Due to the large difference in the electron affinity between and, the holes are bound in an extremely narrow range of the interatomic distance, and even when the concentration is high, the overlapping of the wave functions of the electrons and holes is small, and the decrease in the luminous efficiency is dramatically suppressed. For this reason,
Higher brightness than ever before can be achieved.

FIG. 2 is a schematic configuration diagram showing a growth apparatus used for manufacturing the device of this embodiment. In the figure, 21 is a reaction tube made of quartz, and a raw material mixed gas is introduced into the reaction tube 21 from a gas introduction port 22. The gas in the reaction tube 21 is exhausted from the gas exhaust port 23.

A susceptor 24 made of carbon is arranged in the reaction tube 21, and the sample substrate 27 is used as the susceptor 2.
4. The susceptor 24 is induction heated by the high frequency coil 25. The temperature of the substrate 27 is measured by the illustrated thermocouple 26 and controlled by another device.

Next, a method of manufacturing an LED using the apparatus shown in FIG. 2 will be described. First, the sample substrate 27 (sapphire substrate 11) is placed on the susceptor 24. Gas inlet 2
High-purity hydrogen from 2 is introduced at a rate of 1 l / min to replace the atmosphere in the reaction tube 21. Next, the gas exhaust port 23 is connected to a rotary pump to reduce the pressure in the reaction tube 21 and reduce the internal pressure to 2
Set in the range of 0 to 300 Torr.

Next, after lowering the substrate temperature to 450 to 900 ° C., the H ₂ gas is switched to NH ₃ gas, N ₂ H ₄ gas or an organic compound containing N, for example (CH ₃ ) ₂ N ₂ H ₂ . Together with an organometallic Ga compound, for example Ga
(CH ₃ ) ₃ or Ga (C ₂ H ₅ ) ₃ is introduced to grow. At the same time, if necessary, an organometallic Al compound such as A
l (CH ₃ ) ₃ or Al (C ₂ H ₅ ) ₃ , organometallic I
n compound, such as In (CH ₃ ) ₃ or In (C ₂ H
₅ ) ₃ is introduced and Al and In are added.

When doping is performed, a doping raw material is also introduced at the same time. As a doping raw material, Si hydride for Si, such as SiH ₄ or organometallic S
i compounds such as Si (CH ₃ ) ₄ and organometallic Mg compounds for Mg, such as (C ₂ H ₅ ) ₂ Mg and (C ₆ H
₇ ) ₂ Mg, an organometallic Zn compound for Zn, for example Zn (CH ₃ ) ₂ , Zn (C ₂ H ₅ ) ₂ , an organometallic Cd compound for Cd, for example Cd (CH ₃ ) ₂ , Cd
(C ₂ H ₅ ) ₂ , etc. are used. (Embodiment 2) FIG. 3 is a sectional view showing an element structure of a semiconductor laser according to a second embodiment of the present invention. here,
An n-GaN buffer layer 32 is formed on a 3C (cubic crystal) -SiC substrate 31, and an n-AlGaN cladding layer 33, an As-added GaN light emitting layer 34, and p-A are formed on the n-GaN buffer layer 32.
A double heterojunction structure composed of the lGaN cladding layer 35 is formed. An n-GaN current blocking layer 36 having a stripe-shaped opening is formed on the cladding layer 35 having a double heterojunction structure, and a p-GaN contact layer 37 is formed on the n-GaN current blocking layer 36. A p-side electrode 38 is formed on the contact layer 37, and an n-side electrode 39 is formed on the lower surface of the substrate 31.

With such a structure, by adding As to GaN which is the light emitting layer 34, N atoms in GaN are replaced with As having the same valence, and N atoms and As atoms are replaced. Due to the large difference in the electron affinity between and, the holes are bound in an extremely narrow range of the interatomic distance, and even when the concentration is high, the overlapping of the wave functions of the electrons and holes is small, and the decrease in the luminous efficiency is dramatically suppressed. For this reason,
Higher brightness than ever before can be achieved. (Embodiment 3) FIG. 4 is a sectional view showing an element structure of a semiconductor laser according to a third embodiment of the present invention. This example uses a mixed crystal as a light emitting layer, and the basic configuration is the same as that of the second example.

That is, n-Ga is formed on the 3C-SiC substrate 41.
N buffer layer 42, n-InGaAlN cladding layer 4
3, As-doped InGaN light-emitting layer 44, p-InG
An aAlN clad layer 45 is formed, and n-In is formed thereon.
A GaAlN current blocking layer 46 and a p-InGaAlN contact layer 47 are formed. Both 48 and 49 in the figure are electrodes.

Even with such a structure, the same effects as those of the second embodiment can be obtained. (Embodiment 4) FIG. 5 is a sectional view showing an element structure of a semiconductor laser according to a fourth embodiment of the present invention. This embodiment also uses a mixed crystal as the light emitting layer, and the basic structure is the same as that of the second embodiment.

That is, n-In is formed on the 3C-SiC substrate 51.
A GaAlN buffer layer 52, an n-InGaAlN cladding layer 53, an As-doped InGaAlN light emitting layer 54,
A p-InGaAlN clad layer 55 is formed, and an n-InGaAlN current blocking layer 56 and p-InGaA are formed thereon.
The 1N contact layer 57 is formed. 58 in the figure
59 are all electrodes.

Of course, even with such a structure, the same effects as those of the second embodiment can be obtained. The present invention is not limited to the above-mentioned embodiments. For example, in the examples, As was used as the element to be added to the light emitting layer, but in principle, any atom having the same valence as the N atom may be used, and P, Sb, or Bi as the V group element may be used. it can. Further, B, which is a group III element having the same valence as Ga, can be used as an element substituting Ga instead of N in GaN.

Further, the device structure is not limited to that described in the embodiments, but can be applied to one having a double heterojunction structure using a GaN-based material. In addition, various modifications can be made without departing from the scope of the present invention.

[0028]

As described above in detail, according to the present invention, it is possible to form light emitting centers having high light emitting efficiency at a high density in a GaInAlN layer which is a light emitting layer, and to provide a high brightness short wavelength light emitting element and a green-blue light emitting element. A semiconductor laser can be realized.

[Brief description of drawings]

FIG. 1 is a sectional view showing an element structure of an LED according to a first embodiment.

FIG. 2 is a schematic configuration diagram showing a growth apparatus used for manufacturing the device of the first embodiment.

FIG. 3 is a sectional view showing an element structure of a semiconductor laser according to a second embodiment.

FIG. 4 is a sectional view showing a device structure of a semiconductor laser according to a third embodiment.

FIG. 5 is a sectional view showing an element structure of a semiconductor laser according to a fourth embodiment.

[Explanation of symbols]

11 ... Sapphire substrate 12, 32, 42 ... n-GaN buffer layer 13 ... n-GaN cladding layer 14, 34 ... GaN light emitting layer (active layer) 15 ... p-GaN cladding layer 16, 17, 38, 39, 48, 49, 58, 59 ... Electrode 21 ... Reaction tube 22 ... Gas inlet 23 ... Gas outlet 24 ... Susceptor 25 ... High frequency coil 26 ... Thermocouple 27 ... Sample substrate 31, 41, 51 ... 3C-SiC substrate 33 ... n- GaAlN cladding layer 35 ... p-GaAlN cladding layer 36 ... n-GaN current blocking layer 37 ... p-GaN contact layer 43, 53 ... n-InGaAlN cladding layer 44 ... InGaN light emitting layer 45, 55 ... p-InGaAlN cladding layer 46, 56 ... n-InGaAlN current blocking layer 47, 57 ... p-InGaAlN contact layer 52 ... n-InGaA N buffer layer 45 ... InGaAlN light-emitting layer

Claims (1)

[Claims] 1. A Ga _x Al _y In _1-xy N (0
A semiconductor light-emitting device having a double heterojunction structure in which a light-emitting layer of <x ≦ 1,0 ≦ y <1) is sandwiched between first-conductivity-type cladding layers and second-conductivity-type cladding layers. At least one selected from the group consisting of P, As, Sb, Bi and B is added, and a semiconductor light emitting device is characterized in that an electron trap formed by the added element serves as an emission center.