JPS61107782A - Compound semiconductor device - Google Patents

Abstract

PURPOSE:To reduce the propagation of dislocation from a substrate and the generation of stress-inducing dislocation effectively by forming a high- concentration doping layer in impurity concentration of 2X10<18>atom/cm<3> or more onto the substrate and shaping double hetero-structure onto the doping layer. CONSTITUTION:A high-concentration doping layer 2 in impurity concentration of 2X10<18>atom/cm<3> or more is formed onto a substrate 1. An n type InGaP layer 3, an InGaAsP layer 4, a p type InGaP layer 5 and an n type GaAsP cap layer 6 are shaped onto the doping layer 2 in succession. Accordingly, the propagation of dislocation from the substrate 1 and the generation of stress induced dislocation are reduced effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a compound semiconductor device having a double heterostructure used in a semiconductor light emitting device.

[Conventional technology]

Currently, various research is being carried out on compound semiconductors, mainly in the ■-V group. For example, in the IV group compound semiconductors, there are semiconductor radars, light emitting diodes APD, P in the infrared region to visible region.
GaAs-FET can also be used as a light receiving element such as IN.

Research and development is progressing on high-speed devices such as GaAs1C HEMT. However, these devices are extremely susceptible to dislocation, which affects the light output and life of light emitting devices such as semiconductor radars and light emitting diodes, and causes S as noise in light receiving devices such as APDs and PINs.
It affects the N ratio, and affects the threshold voltage of high-speed devices such as MES-FETs.

These dislocations include those inherited from the compound semiconductor crystal substrate and those introduced during epitaxial growth, process, or device operation.

Compound semiconductor crystal substrates have more dislocations than S1 crystal substrates, for example, GaAs substrates usually have 1 to 5xlO'3
That's about it. It is known that when epitaxial growth is performed on such a substrate, dislocations in the substrate are carried over to the epitaxial layer as they are under normal conditions.

In the double heterostructure used in semiconductor light emitting devices, problems arise not only from dislocations from the substrate but also from dislocations caused by lattice mismatch at the hetero interface and dislocations caused by differences in thermal expansion coefficients.

[Problem that the invention seeks to solve]

Regarding misfit dislocations caused by lattice mismatch, for example, regarding InGaAsP on InP, the Research and Practical Application Report of the Institute of Telecommunications Vol. 28, A6
As described in P1027-42 (1979), the lattice constant difference in the direction parallel to the shrimp layer surface is 0.03%.
Misfit dislocations are introduced to a certain extent. Particularly in the case of a complex multilayer structure, it is difficult to control the composition so that all the layers are perfectly lattice matched.

Regarding the influence of thermal expansion coefficient, Physica Status Solid 4 (Phyi, 5tat, Sol, (a
) 53, 1651979),
Since the coefficient of thermal expansion differs depending on the composition, stress is generated due to the thermal history during the process, which tends to cause dislocation.

Regarding dislocations that occur between the semiconductor surface and the electrode on it, the difference in thermal expansion coefficient between the ■-V group compound semiconductor and the electrode metal is generally very large, and the stress generated is This is extremely large compared to thermal stress. This indicates that dislocations are likely to occur between the semiconductor surface and the electrode during the process.

However, at present, countermeasures against these problems have not been studied much, other than using a substrate with as few dislocations as possible or trying to match the lattice constant in multilayer epitaxial growth.

Next, a double heterostructure for a semiconductor radar will be described in detail as an example of a compound semiconductor device used in a semiconductor light emitting device.

FIG. 6 shows a cross-sectional view of a typical double heterostructure. Here, a GaAs substrate is used and an In-Ga-As-P semiconductor radar having an emission range of 0.7 μm band is shown.

In the figure, 1 is a GaAs substrate, 3 is an InGaP cladding layer, and 4 is a GaAs substrate.
ij is an InGaAsP active layer, and 5 is an InGaP cladding layer.

The dislocation density in the GaAs substrate 1 used as the substrate here is usually about 1 to 5×10'c+n'. If a double heterostructure is created on such a substrate, only an epitaxial layer can be obtained which takes over dislocations from the substrate and has a dislocation density comparable to that of the substrate.

In addition, when creating a double heterostructure, 700
Since crystal growth is carried out at a high temperature of about 800 DEG C., the crystal undergoes thermal contraction and distortion while being cooled down to the chamber after growth.

This strain is caused by the difference in the thermal expansion coefficient of each layer, and the GaAa substrate and the InGaP substrate have the largest difference in thermal expansion coefficient.
Large thermal strains occur between the layers, causing stress-induced dislocations. As a result, the dislocation density of the epitaxial layer having a double heterostructure becomes higher than that of the substrate.

An object of the present invention is to provide a compound semiconductor device with reduced dislocations.

[Means for solving problems]

The present invention provides a compound semiconductor device having a double heterostructure used in a semiconductor light emitting device, with an impurity concentration of 2.
×10 atoms/c! A compound semiconductor device characterized in that a high concentration doping layer of rL3 or more is provided on a substrate, and a double heterostructure is formed on the doping layer, and
A compound semiconductor device having a double heterostructure used in a semiconductor light emitting device is characterized by having a highly doped layer with an impurity concentration of 2×10 atoms/cm” or more under an electrode on an epitaxial layer formed in the device. In a compound semiconductor device and a compound semiconductor device having a double hetese structure, an impurity concentration of 2×10
A highly concentrated doping layer of atomic layer or higher is provided on the substrate,
A double heterostructure is formed on the doped layer, and an impurity concentration of 2×10 is formed with ′ on the epitaxial layer side as a seed.
The present invention is a compound semiconductor device characterized by having a highly doped layer with a concentration of atoms/cwt" or higher.

The present invention will be explained below with reference to the drawings.

The present invention proposes a compound semiconductor device having a highly doped layer 2 with an impurity concentration of 2×10 18 atoms/min 3 or more in a double heterostructure as shown in FIG.

In FIG. 1, the high concentration doping layer 2, n-type InGaP layer 3, InGaAsP layer 4, and p-type InGaP layer 5 are successively formed on a GaAs substrate l.

Here, the journal Applied Physicians (J, Appl, Phys, 49) by Doug Gund and Seki et al.
(2) (1978) 822) is an impurity with a large single-gen do energy, and the n-type dopants include S, Se, and Te.

Zn is used as Sl and p-type donokund, and B, At, N, etc. are used as neutral impurities of Cd1.

These impurities have an impurity concentration of 2×10 atoms/cm3
In the DH structure for radar having a highly doped layer as described above, dislocations are more reduced than in the substrate. The reason for this is thought to be that these impurities are incorporated into the crystal at a high concentration, which increases the critical shear stress of the crystal, making it difficult for dislocations to occur and for the generated dislocations to be difficult to propagate.

〔Example〕

Examples of the present invention are shown below.

(Example 1) A double heterostructure for a semiconductor radar was created using an InGaAsP mixed crystal on an n-type GaAs substrate, and its proportionality will be explained based on FIG.

1 in the figure is an Sl-doped n-type GaAs substrate, the carrier concentration is] x 10"cIn-3, and the dislocation density is Fi1 x 1.
There are 0'an-2te.

On top of this, an InGaP high concentration doping layer 2 doped with 5x1018 cm-3 of S by vapor phase growth is formed.
After that, S was grown to a thickness of 8X10"c++t-' as in the conventional double heterostructure for semiconductor radar.
Doped 1, n-type InGaP layer 3 with a thickness of 1 μm, non-doped I
nGaAaP active layer 4: 0.11 m %Zn: 1×10
cIrL doped p-type InGaP layer 5
n-type GaAs doped with 5×10 − 1 μm% S
The P cap layer 6 was successively grown to a thickness of 5 tones. The lattice constants of each grown layer are lattice matched to within 5 x 10''-'.

As a result of examining the dislocation density of the cap layer 6 by KOH processing and chipping, it was confirmed that the dislocation density was extremely low at 300 cIrL, and that propagating dislocations from the substrate and stress-induced dislocations were significantly reduced. .

Furthermore, the results of a similar experiment using the prior art where only lattice matching was taken into account showed that the dislocation density was approximately 15,000 cWL-2, which indicates that the present invention is extremely useful for optical devices and high-speed devices that are easily affected by dislocations. It's expensive.

(Example 2) GaAs for light emitting diodes in which n-GaAaP mixed crystal was grown epitaxially on an n-type GaAs substrate.
An example in which a double heterostructure for a semiconductor radar is created using a P-striped substrate will be explained based on FIG. 3.

1 in the figure is an n-type GaAm substrate on which about 30 μm of S
n-type GaA s doped with lXl0 crn
1-XP
) A core stand layer 8 is provided.

S on the GaA+sP shrimp substrate for light emitting diode
An InGaP heavily doped layer 2 doped with 5 x 1018 crIL-' is grown to 2 μm, and then S is grown to 13 x 10 c as in the conventional double heterostructure for lasers.
m doped n-type 1nGaP layer 3 to 1. □
% non-doped InGaAsP active layer 4 with 0.1μ, Zn
A p-type InGaP layer 5 doped with 1×10 cIrL and a 5×10 m S-doped n-type GaAaP layer 9 were successively grown to a thickness of 51rrrL.The lattice of each grown layer The constant is 5
It is lattice matched to within I O-'.

The dislocation density of the cap layer is H2S04 (96chi): H,P
O4 (85 inches): H20□ (30 inches) = 5:5:2, and as a result of 50.000 cm of 50.000 cm after photo-sound irradiation with tinda solution and tinging. The dislocation density of the GaAsP epitaxial substrate itself for light emitting diodes was similarly investigated and was found to be 350,000 to 400,000 cm.
Met. In addition, the results of a similar experiment using the conventional technology that focused only on lattice matching showed that the dislocation density was 400.0O
It became OcrrL.

These results confirmed that propagating dislocations and stress-induced dislocations from the substrate were significantly reduced by the highly doped layer.

(Example 3) An example of fabricating an inner stripe semiconductor laser using an InGaAsP mixed crystal on an n-type GaAs substrate will be described with reference to FIG.

In the IH8I-doped n-type GaAs substrate in the figure, the carrier concentration is lXl0"cm-3, and the dislocation density is u IX 1.0'
It is art-2.

N-type InGa doped with 8xlOan of S on this
P cladding layer 3 is 1lrrrL% non-doped InGa
AsP active layer 4 is 0.11InL, Zn is 1Xl0
cnt doped p-type I nGaP layer 5t
An n-type blocking layer 10 doped with 8×10 cm of l-IItrrL1S was grown to a thickness of 0.5 μm, respectively. Here, the n-type block layer 10 has a width of 4 as shown in the figure.
Etching is done in a stripe shape that is about the same size as the voice, and then Z
InGaPnGa doped with 1×10 cIrL n
P crystal 1rrL was grown, and Zn was further added to 5×10 cI.
rL Doped GaAs GaAs doped with one high concentration doping layer 12 and one Zn layer 018c'i-'
Each contact layer 13 was grown to a thickness of 0.3 μm. The lattice constants of each grown layer are lattice matched to within 5 x 10-'. The electrode is p-type, the Au-Zn alloy electrode 14 that also serves as a heat sink is 5000i, and the n-type is Au.
Electrode 15 was deposited to a thickness of 100×.

The inner stripe type semiconductor laser produced in this manner continuously oscillated at room temperature at an oscillation wavelength of 7800X, and had an oscillation threshold current density of 2 kA/cIn2. A lifespan test of this Rede was conducted at room temperature by passing a current 1.5 times the oscillation threshold current, and as a result, the average lifespan was about 3000 hours.

On the other hand, the life test result of the prior art inner stripe type semiconductor radar without the heavily doped layer 12 was about 800 hours on average.

This is thought to be due to a considerable amount of stress-induced dislocation occurring during the creation of the p-type electrode, and the highly doped layer 12
It is considered that the provision of this makes it difficult for generated dislocations to propagate to the active layer 4.

As described above, the present invention is also useful against stress-induced dislocations that occur during the process, and is effective for high-speed devices and optical devices that undergo complicated processes and thermal history.

(Example 4) Grade n-type GaAsP mixed crystal on an n-type GaAs substrate.

Rad epitaxially grown GaA for light emitting diodes
An example of forming a mesa stripe type semiconductor radar on an sP epitaxial substrate will be explained based on FIG.

This is an 11rin type GaAs substrate in the figure. On top of this
S-doped n-type GaAttr 1− xP x (0<x< O
-4) Graded layer 7 and S of about 30 μm
n-type GaAs doped with lXl0"cm-3, -,
Px (X: 0.4) constant N! I8 is provided.

On such a GaAsP epitaxial substrate for a light emitting diode, 2 μm of InGaP doped with 5×10 cm of S doped/e2 was grown, and then S was grown to 8×10”cIrL-' in the same manner as the conventional double heterostructure for a laser.
Doped fan-type InGaP cladding M3 is 17 m, non-doped InGaAsP active layer 4 is Q, L, Zn is 1.
×10 crrL doped p-type InGaP layer 5 is grown to 1 μm, and further Zn doped 5×10 crrL p-type 1nGaP high concentration doping layer 12 is grown to 2p.
m, f3 doped n-type I with 5×1717 crrL-3
An nGaAsP layer 16 was grown to a thickness of 1 μm. Thereafter, Zn was selectively diffused from the bottom of the cap with a stripe width of 4 to form a Zn diffusion layer 17, and a mesa structure was etched. After a mask 18 was formed at 5102, Au was evaporated to form an electrode 15.

The mesa stripe type semiconductor laser created in this way oscillated at room temperature at an oscillation wavelength of 6500X, and the oscillation threshold current density was 4 kA/cm2.In contrast, n-type high concentration doping using conventional technology The characteristics of the mesa stripe type semiconductor radar without the layer 2 and the p-type cavity concentration doped layer 12 are as follows: The oscillation threshold current density is 12 at room temperature pulse oscillation.
kA/an”.

This is considered to be because the highly doped layer according to the present invention inhibits the generation and propagation of dislocations, and is highly useful for semiconductor light emitting devices that are easily affected by dislocations.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to effectively reduce the propagation of dislocations from the substrate and the generation of stress-induced dislocations, which is an extremely excellent effect when considering optical devices and high-speed devices that are easily affected by dislocations. Obtainable.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the basic structure of the present invention, FIGS. 2 to 5 are sectional views showing embodiments of the invention, and FIG. 6 is a sectional view showing a conventional compound semiconductor device. l...GaAs substrate, 2...highly doped layer,
3...n-type 1nGaP layer, 4-InGaAsP layer,
5-p-type 1nGaP layer, 12... p-type cavity concentration doped layer, 14... Au-Zn alloy electrode, 15... electrode. Figure 1 Figure 2

Claims (3)

[Claims] (1) In a compound semiconductor device having a double heterostructure used in a semiconductor light emitting device, an impurity concentration of 2×
1. A compound semiconductor device, characterized in that a high concentration doping layer of 10^1^8 atoms/cm^3 or more is provided on a substrate, and a double heterostructure is formed on the doping layer. (2) In a compound semiconductor device having a double heterostructure used in a semiconductor light emitting device, an impurity concentration of 2×10
A compound semiconductor device characterized by having a high concentration doping layer of ^1^8 atoms/cm^3 or more. (3) In a compound semiconductor device having a double heterostructure used in a semiconductor light emitting device, an impurity concentration of 2×
A highly doped layer with a concentration of 10^1^8 atoms/cm^3 or more is provided on the substrate, a double heterostructure is formed on the doped layer, and an impurity concentration of 2 x 10^1 is formed under the electrode on the epitaxial layer side. A compound semiconductor device characterized by having a high concentration doping layer of ^8 atoms/cm^3 or more.