JPS61203691A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To obtain the semiconductor light emitting device capable of continuous oscillation at room temperature by forming an epitaxial layer of double hetero structure of In-Ga-As-P group on a GaAsP graded epitaxial wafer. CONSTITUTION:On the wafer in which a GaAs1-XPX (X:0.4) mixed crystal is grown on a GaAs bulk crystal by the graded epitaxial growth, a semiconductor laser doped with Si, S, and Se is formed as an N-InGaP clad layer. The semiconductor layer fabricated from the wafer doped with Si by using SiH4 can not offer pulse oscillation at room temperature. The laser doped with S by using H2S can offer pulse oscillation at room temperature with an oscillation threshold current density of Jth=35-60KA/cm<2>. Meanwhile the semiconductor laser fabricated from the wafer doped with Se by using H2Se can offer pulse oscillation at room temperature with an oscillation threshold current density of Jth=3-13 KA/cm<2>. The laser of low Jth offers the continuous oscillation at room temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor light emitting device using a GaAsP graded epitaxial wafer.

[Prior art and its problems]

In-Ga-As-P mixed crystals can have various forbidden band widths (from 0.36 eV for InAs to 2.25 eV for GaP) by changing the composition, and can be used in the infrared region. It can be considered to be used as optical devices such as laser diodes, light emitting diodes, and light receiving elements in the visible range. However, the bulk crystal that serves as the substrate is In
P, GaAs, GaP.

Since it is very difficult to create anything other than binary InAs compounds, the mixed crystals that can be epitaxially grown on these substrates are also limited to crystal compositions whose lattice constants match those of these substrates. In the above-mentioned quaternary mixed crystal, the forbidden band width is 0.75 eV to 1.28 when an InP substrate is used.
eV, the forbidden band width is 1.4 when using a GaAs substrate.
It is limited to mixed crystals in the range of 3 eV to 1.88 eV.

However, in recent years, with the development of graded epitaxial growth technology, it has become possible to expand the range of the forbidden band width using bulk substrates that can be easily handled manually. This is G
Ga A 5l-x on aP or GaAs substrate
Px (0≦X≦1), a graded layer whose composition changes continuously or stepwise, and GaAS+-xPx (
A constant layer with a constant composition of 0 < x < 1) is grown, and by forming a pn junction in this constant layer, a light emitting diode with a wavelength that cannot be achieved with binary bulk crystals is obtained. (For example, Japanese Patent Publication No. 58-43898 published by Mitsubishi Monsando ``Method for vapor phase growth of compound semiconductor single crystal thin film'').

Furthermore, graded epitaxial technology uses a mixed crystal substrate that has a lattice constant that is not found in binary bulk crystals, and epitaxially grows a double heterostructure of In-Ga-As-P mixed crystals on the substrate. It is expected that it will be applied to

However, In-Ga-As-P semiconductor lasers fabricated using GaAsP graded pitaxial wafers have a problem that their oscillation threshold current is high and continuous oscillation at room temperature is currently difficult (for example, Fujimoto et al.
ujimoto et al.) Japan Journal of Applied Fixtures (Japan Jo
urnal of Applied Physics)
21 (1982) 488). This is also due to the presence of misfit dislocations, strain in the epitaxial layer, and lattice plane tilt, which are characteristic of GaAsP graded epitaxial wafers (Usui, Matsumoto, 1984 Spring 31st Applied Physics Association Lecture proceedings P609
), it was found that the crystallinity of the n-type cladding layer is partly responsible for the above. This result is consistent with previous reports that when the luminous efficiency of the cladding layer is low, the threshold current increases, for example in the case of a laser (W, T, Tang).

Applied Fixtures Letter (Appl, Phys
.

Shett, ), 33.245 (1978))
.

[Purpose of the invention]

The purpose of the present invention is to eliminate such conventional drawbacks and to
An object of the present invention is to provide a semiconductor light emitting device in which an In-Ga-As-P double heterostructure epitaxial layer with good crystallinity is grown on an aAsP graded epitaxial wafer.

[Structure of the invention]

The present invention provides GaAsl on GaP or GaAs crystal.
-xPx (0 < This semiconductor light emitting device has a double heterostructure layered structure, and is characterized by doping Se as an impurity in an n-type cladding layer.

[Detailed explanation of the configuration]

As n-type dopants for group (1)-(2) compound semiconductors, group (2) elements that substitute for group (2) atoms and group (2) elements that substitute for group (2) atoms are generally known. When creating a double heterostructure for a semiconductor laser using the vapor phase growth method, the requirements for an n-type dopant are that the dopant must first be supplied in a gaseous state, be stable at room temperature, and adhere to the tube wall even if it decomposes during growth. It must also meet the following requirements: and be difficult to re-evaporate. N-type dopants that satisfy this condition include hydrides such as H2S, H2Se, and SiH.

can be considered. As a result of repeated research on n-type 1nGaP or InGaAsP layers grown on GaAsP graded eviaxial wafers by vapor phase growth, the present inventors found that among these, H
It has been found that 2Se best satisfies the above conditions.

Here, G
G a A S I-x Px (X
The structure of the present invention will be explained in more detail with reference to FIGS. 2 and 3, taking as an example a case where a graded epitaxial wafer is used. In addition, Fig. 2 shows GaAs, -XPx (X
: 0.4) I 711-YG ayP (y2O,7) grown on graded epiximal em.
layers using H2S, H2Se, and SiH<S gases, respectively.

FIG. 4 is a characteristic diagram showing doping efficiency when doping with Se and Si. Also, Figure 3 shows S.

FIG. 2 is a characteristic diagram showing the photoluminescence emission intensity of an n-InGaP layer doped with Se and Si.

Ink-yG was grown on a GaAS+-xPx (x: 0.4) graded epitaxial wafer by vapor phase growth.
When growing the ayP (y: 0.7) layer, if SiH gas is used as the n-type dopant, Si
The impurity is ■711-YG ayP (y: 0.7)
Carriers are generated as n-type impurities in the layer (see Figure 2), but when photoluminescence is measured, the photoluminescence emission intensity is very weak (see Figure 3). Sl as an impurity
It is inappropriate to use In addition, when H2S gas is used, the doping efficiency is about one order of magnitude lower than that of Se using H2Se, as shown in Figure 2, and when photoluminescence is measured, the photoluminescence emission intensity is 1 digit lower than that of Se using H2Se. /2 or less, and the carrier concentration required for the n-cladding layer of a double heterostructure for semiconductor lasers: If it is more than 10"an-', it will be weaker than 1/3 compared to Se. Also, if S is lQ I II cm '″
It was confirmed by photoluminescence measurement in 77 that doping of 3 or more forms a deep level.

Compared to these S and Si, Se using H2Se has better doping efficiency as shown in Figure 2, and the photoluminescence emission intensity as shown in Figure 3. IQ used: 18 c
It was found that the most intense light emission occurs at a carrier concentration of about m −3.

As described above, InGaP or I
In a semiconductor light emitting device with a double heterostructure in which nGaAsP is used as a cladding layer and InGaAsP or GaAsP is used as an active layer, S is used as an impurity in the n-type cladding layer.
By doping with e, a semiconductor light emitting device with good crystallinity can be obtained.

〔Example〕

In this example, GaAs1-xP is placed on the GaAs bulk crystal.
Semiconductor lasers were prepared by doping Si, S, and Se as n-1nGaP cladding layers on wafers on which x (X: 0.4) mixed crystal was grown by graded epitaxial growth, and comparisons were made.

For growth, hydride vapor phase epitaxy is used, and the structure is
As shown in the figure. The GaAsP graded epitaxial substrate has a mixed crystal composition of about 30 μm thick as a graded epitaxial layer 2 on a GaAs bulk single crystal with a thickness of about 300 μm as a bulk single crystal 1.
:0) to GaAS+-xPx (x: 0.4) little by little, and a constant layer 3 on top of which GaAS 1-xPx (x:
A layer having a constant mixed crystal composition of 0.4) is epitaxially grown. Therefore, on the constant layer 3 is an n-cladding layer 4 which becomes a double heterostructure for semiconductor lasers.
As, an n-InGaP layer with a layer thickness of 2 μm, an InGaAsP layer with a layer thickness of 2000 nm as the active layer 5, a p-InGaP layer with a layer thickness of 2 μm as the p-cladding layer 6, and an InGaAsP layer with a layer thickness of 1 μm as the cap layer 7. grew sequentially.

Here, the p-InGaP cladding layer 6 has Zn of 1×101
It is doped to about 8 cm-3. InGaAsP
Active layer 5 and cap layer 7 are non-doped. n-
The InGaP cladding layer 4 was prepared by doping S using H2S, Si doping using S i Ha, and Se doping using H2Se. All carrier concentrations are I x IQ18
It is about cm-3.

Using these double heterostructure wafers for semiconductor lasers, a Zn-diffused planar stripe semiconductor laser with a stripe width of 18 μm was prototyped, pulsed at room temperature, and the oscillation threshold current densities were compared.

A semiconductor laser fabricated from a double heterostructure wafer for a semiconductor laser doped with Si using SiH did not produce pulse oscillation at room temperature.

A semiconductor laser fabricated from a double heterostructure wafer for a semiconductor laser doped with S using H and S has an oscillation dark current density J th = 35 to 60 K at room temperature.
Pulse oscillations were obtained at A/caf.

On the other hand, a semiconductor laser fabricated from a double heterostructure wafer for a semiconductor laser doped with Se using H2Se according to the present invention can oscillate pulses at an oscillation threshold current density Jth = 3 to 13 K A / cnf at room temperature. was obtained, and continuous oscillation at room temperature was obtained with a laser with a low Jth.

As described above, in a semiconductor light emitting device having a double heterostructure, which is fabricated using a GaAsP graded epitaxial wafer by a vapor phase growth method and has a cladding layer of InGaP or InGaAsP and an active layer of InGaAsP or GaAsP, impurities in the n-type rad Se was doped as follows. It has been established that semiconductor light emitting devices are extremely useful.

〔Effect of the invention〕

As explained above, according to the present invention, In-
By forming a Ga-As-P double heterostructure epitaxial layer, it has become possible to obtain a semiconductor light-emitting device capable of continuous oscillation at room temperature.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view showing a double heterostructure for a semiconductor laser created on a mixed crystal graded epitaxial substrate.
-xP,, (x : G, 4) A characteristic diagram showing the doping efficiency when doping is performed using H4 gas on the InGaP layer grown on the graded epitaxial wafer. , Figure 3 shows S, S
FIG. 4 is a characteristic diagram showing the photoluminescence emission intensity of an n-1nGap layer doped with e and Si. 1... Binary bulk single crystal 2... Graded epitaxial layer 3... Constant epitaxial layer 4... N-cladding layer 5... Active layer 6... P-cladding layer 7...・Cap layer

Claims (1)

[Claims] (1) GaAs_1_ on GaP or GaAs crystal
Using a GaAsP graded epitaxial wafer on which a −_xP_x (0<x<1) mixed crystal is epitaxially grown, InGaP or In produced by a vapor phase growth method on the GaAsP graded epitaxial wafer is used.
It is a semiconductor light emitting device with a double hetero structure in which GaAsP is used as a cladding layer and InGaAsP or GaAsP is used as an active layer, and Se is used as an impurity in the n-type cladding layer.
A semiconductor light emitting device characterized by being doped with