JPS60202926A - Epitaxial wafer - Google Patents

Abstract

PURPOSE:To improve the quality of a crystal, and to increase luminance by forming an ND slow reducing layer in an indirect transition type gallium phosphide arsenide epitaxial wafer for a light-emitting diode. CONSTITUTION:A GaP epitaxial layer 2, a GaAs1-xPx (0<1-x<=0.5) arsenic component composition ratio increasing layer 3 and a GaAs1-xPx (0<1-x<=0.5) composition constant layer 4 are formed on a GaP single crystal substrate 1, and an ND slow reducing layer 5, ND therein is reduced gradually up to desired low concentration B from high concentration A, and an ND constant layer 6, ND therein is fixed in desired low concentration B, are shaped on the layer 4. According to such constitution, the quality of a crystal can be made better than conventional epitaxial wafers, ND therein is altered steeply to low concentration B from high concentration A, thus improving luminance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides indirect transition type gallium arsenide phosphide (GaAsx-xPx + 0 < i-x
≦0.5) Regarding epitaxial wafers.

Gallium phosphide (G
aP) with an arsenic component composition ratio of 1-X (1
Conventionally, a device provided with an indirect transition type gallium arsenide phosphide (GaAs1-XPx) epitaxial film in the range <i-x≦0.5 has been used.

The present inventors proposed a method of adding nitrogen as an isoelectronic trap in order to obtain practical luminous efficiency when manufacturing light emitting diodes using this epitaxial wafer (March 6, 1980). (Japanese Patent Application) When adding nitrogen, GaAs 1. K
N-type impurity concentration (hereinafter referred to as ND) in the PX epitaxial film
It is being carried out to lower the concentration (about 1 x 10 atoms/i) from a high concentration (about 1 x 10 atoms/m) to a low concentration (about 1 x 10 atoms/i) (see Figures 1-1 and 1-2). If only to increase the carrier injection efficiency, it is sufficient to set the ND to about 1 x 10 atoms/d over the entire epitaxial film, but with this low ND, the forward rise voltage V of the light emitting diode is too high, causing a practical problem. In order to achieve this, the above-mentioned ND distribution is adopted.

GaASl, cPx (0<1-x≦0
．． 5) To explain the growth of epitaxial film using drawings, Figure 1-1 shows GaAs t-x for yellow light emitting diode.
An example of a cross-sectional view of a px epitaxial wafer is shown in Figure 1.
-2 is its ND distribution and nitrogen concentration (hereinafter referred to as NN)
An example of the distribution is shown.

In Figures 1-1 and 1-2, 1' is a GaP single crystal substrate with a thickness of approximately 300 microns φ), and 2' is a GaP single crystal substrate with a thickness of 5 μm.
P epitaxial layer 3' is a GaAs 1-x px layer with increased arsenic composition ratio of 35 μm in which the arsenic composition ratio 1-X is increased from 0 to about 0.15 using a crystal misalignment strain relaxation technique, 4 has a constant thickness of 15μ with 1-X of approximately 0.15
C) aAs P composition - Window layer, Go-XX and 6' are GaAs P groups doped with nitrogen atoms -
xx is a growth window layer (however, the crystal composition is the same as layer A), and 5
' is a window layer, which is a gradually increasing layer of NN with a thickness of 5 μm, in which <NN is gradually increased from O to a desired value, as shown in FIGS. 1-2. However, in this method, as shown in FIGS. 1-2, the concentration of ND is abruptly changed from high to low concentration in the ileum after the formation of layer 5' begins.

The present inventors have discovered that GaAs doped with at least nitrogen atoms
Composition of 1-XPX - In the window layer, lowering the ND in the layer not only has the effect of increasing the carrier injection efficiency, but if this is not sharply reduced, GaAs 1-X
Focusing on the effect of improving the crystal quality of the PX layer, the present invention was achieved as a result of repeated research to obtain an indirect transition type GaA3□-x"x epitaxial film for light-emitting diodes with high crystal quality. It is something.

That is, nitrogen atoms and n-type impurities (sulfur S, tellurium Te) are usually used as isoelectronic traps.
etc.) are both substituted at the group II atom position of the ternary compound hemihyposome GaA31-xpx crystal, so when nitrogen atoms are added to this crystal, NDs are added at the lowest possible concentration (radiative recombination). However, research has revealed that if the ND is reduced too rapidly, the effect of improving crystallinity is weak. In order to effectively exhibit the low concentration effect of the n-type impurity, the following method is used:
10 atoms/d) to a low concentration (approximately 1 x 6 10 atoms/d) in the initial stage, the concentration of ND is gradually decreased. By providing the ND thin layer having a layer with a constant value, it is possible to obtain a wafer having a GaAs1-x pX epitaxial film of crystalline quality, thereby achieving an improvement in the brightness of the light emitting diode.

Regarding the addition of nitrogen atoms, if they are added too quickly, crystal defects etc. will rapidly increase and the crystal quality will deteriorate.To prevent this, in the initial stage of nitrogen atom addition, NN is gradually increased to a desired value. It is necessary to provide a gradually increasing layer.

This will be explained in detail below with reference to the drawings. Although GaP alone may be used as the single crystal substrate in the present invention, a GaP single crystal substrate having an epitaxial layer of GaP may also be used.

Figure 2-1 shows oaA8 for yellow light emitting diode according to the present invention.
1- x Px Cross-sectional view of epitaxial wafer 1
As an example, FIG. 2-2 shows an example of the ND distribution and NN distribution. Although layers 1 to 4 in FIGS. 2-1 and 2-2 have the same composition and thickness as layers 1' to 4' in FIGS. 1-1 and 1-2 according to the conventional method, this explanation is omitted. do. Layer 5 is a 5μ thick ND gradually decreasing layer (
During the formation of this layer, as shown in Figure 2-2, NN is gradually increased from 0 to a desired value), layer 6 is a 20μ thick ND-window layer with ND fixed at a desired low concentration B ( The present invention will now be explained based on Examples and Comparative Examples, but it goes without saying that the present invention is not limited to these Examples. be.

[Example 1] GaAs1- for yellow light emitting diode was prepared by the following method.
'X PX Ebitaki V Yaruuehe was manufactured.

GaP single crystal with tellurium (Te) doped with 2.3XIQ atoms/cIl crystal orientation <100> from (1υυ)<
After slicing to a thickness of 350 μm with a 5° deviation in the direction of 110>, a GaP layer with a thickness of about 300 μm was used as an epitaxial substrate after being subjected to conventional chemical etching and mechanochemical polishing. .

In addition, hydrogen (H2) is used as a reaction gas, and the concentration of hydrogen dilution is 5
(1 ppm hydrogen sulfide (H2S, n-type impurity),
1% hydrogen arsenide (AsH3) in H2 dilution, 1% in H2 dilution
0% hydrogen phosphide (PHa), high purity hydrogen chloride gas (EO
l) and high purity ammonia gas (NHs).

Thereafter, the above reaction gases were converted to H2, H28/H2, AsH, respectively.
a/H2.

Abbreviated as PH3/H2, HOI and NH.

After cleaning the GaP single crystal substrate, the ()aP single crystal substrate and the high-purity Ga-containing quartz container are set at a predetermined location in the vapor phase epitaxial reactor.

After introducing high-purity nitrogen gas (N) and then high-purity hydrogen gas (H2) as a carrier gas into the reactor to sufficiently replace the inside of the reactor, temperature elevation was started.

After confirming that the temperature of the GaP single crystal substrate set area has reached 880℃, the Ga”O for yellow light emitting diode is
, ts Po, ss vapor phase growth of epitaxial films was started.

First, H2S/H was introduced at a flow rate of 5 Qcc/min, and on the other hand, HOI was introduced at a flow rate of 45 cc/min to react with Ga in the quartz container to form Gaol, and at the same time, HOI was introduced at a flow rate of 250 ee/min. GaP with PH37H2
A GaP epitaxial layer 2 was grown on a single crystal substrate.

Next, a layer 3 with an increased arsenic composition ratio was grown on the GaP epitaxial layer 2. First the H2S/H
2. HOI and PH3/H2 flow rate each 50cc
/min, 45Ce/min and 25Uee/min while increasing the flow rate of ABH,/H2 from occ1 min to 260cc/min.
The arsenic composition ratio increased layer 3 in which 1-X varied from 0 to about 0.15 was formed by gradually increasing the arsenic content to 0.15. ASH
3/H, while the flow rate changes from Occ/min to 170ce/min, the temperature of the board setting area is changed from 880°C to 820°C.
gradually and continuously decreased. From then on, the temperature of this substrate set area was kept at 820°C until the epitaxial growth was completed.
Fixed.

Then, the above H2S/H2, HOI, PH3/H2
and AsH3/H2 flow rates were 5 Q Ce 7 min, 45 C, C 7 min, 250 CC/min and 260 C, respectively.
GaAs 17'X PX composition-electrical layer 4, ie, 0.15 PO, 115 layer, was grown at a fixed speed of 2.3 m/min.

Next, HOI, PH3/H2 and AsH3/H2 were diverted at 45 cc/min, 250 eC/min and 260 eC/min, respectively.
cc/min, the flow rate of
fl Q cc was gradually increased up to 7 minutes using the changes shown in FIG. 3 to form a <No gradual decreasing layer 5 according to the present invention. Finally, H2S/H2, HOl, PH8/
H2゜ASH3/H2 and NH3 flow rates are each IQc
c/min, 45cc/min, 25oc/min, 260cc/min
ND constant GaAs P doped with n-type impurities and nitrogen atoms to the desired concentration fixed at 400 CC/min.
-XX Composition - The electrical layer 6 was formed, and the growth of the indirect transition type GaAs1-x px epitaxial film for yellow light emitting diodes was completed to obtain an epitaxial wafer.

[Example 2] GaA8o, 15Po, a
5 epitaxial wafer 8 was prototyped.

[Example 3] GaA30.11tP0.
A 85 epitaxial wafer was prototyped. As is clear from the figure, the first 10μ of layer 4 has a flow of H2S/H2 of 5
Although it was constant at 0 CC/min, the next 5 μ was gradually changed.

[Example 4] GaAs o, □5"O, a was produced under the same conditions as in Example 1 except that the method of introducing H28/H2 was changed as shown in FIG.
5 epitaxial wafer 8 was prototyped. As is clear from the figure, Jl:! The flow rate of H2S/H2 was kept constant at 50 CC/min for the first 10μ of j4, or was introduced while changing the flow rate for the next 5μ as shown in the figure.

[Comparative example]

As shown in FIG. 7, GaAs, 1°PO
,85 epitaxial wafer was prototyped.

Next, Zn was diffused into the wafer to form a P-N junction to produce a yellow light emitting diode.The brightness (millicandela, mad) of this yellow light emitting diode (without resin coating) was as shown in Table 1. Met.

Table 1 * Forward current density: 10 A/m Luminance value = average of 10 runs As shown in Table 1 above, the ND removal gradual reduction method Examples 1 to 4) of the present invention are based on the breathable Kosho method ( Approximately 20% compared to comparative example)
This coupled with the improvement in brightness, confirming the effect of the method of the present invention.

[Brief explanation of the drawing]

Figure 1-1 shows GaAs for yellow light emitting diode made by conventional method.
, - Cross-sectional view of xPx epitaxial wafer, Figure 1-
2 is an explanatory diagram showing the ND distribution and NN distribution for the quay, and FIG. 2-1 is an explanatory diagram showing the ND distribution and NN distribution for the quay.
)aAs t -xPx A cross-sectional view of an epitaxial wafer, FIG. 2-2 is an explanatory diagram showing the ND distribution and N distribution of the wafer. In addition, Figures 3.4.5.6 and 7 show n-type impurity (H2S/Hz) and ammonia gas (NH
It is an explanatory view showing the introduction method of a). 1.1...GaP single crystal substrate 2.2...GaP epitaxial layer 3.3...()aAs, -xPx increasing arsenic composition ratio layer 4.4...GaAs, xPX constant composition layer (However, the final 5μ in Figures 5 and 6 is the ND gradually decreasing layer)5
．． 5...NN gradually increasing GaAs 1-XPx composition constant (
- (However, in the case of Fig. 3.4, the ND gradually decreasing layer, in the case of Fig. 7, the No rapidly decreasing layer) 6.6... NN constant GaAs where ND is constant at low concentration
t-x Px constant composition layer A, A... Desired n-type impurity high concentration value B, T... Desired n-type impurity low concentration value C2d... Desired island value Patent applicant Shin-Etsu Semiconductor Co., Ltd. 1 ■ Figure 3 @ 'BJ4

Claims (1)

[Claims] 1. Arsenic component composition of a compound semiconductor single crystal substrate consisting of Groups 1 and V of the periodic table, an epitaxial layer consisting of the same components as the substrate, and ternary compound semiconductors GaAs and -EPx rate increasing layer (however, g<t-X≦05), GaAa
1-xPx composition ratio constant M (however, Q<1-z≦0.5
) and composition of GaAs□-XPx doped with nitrogen atoms in the radiative recombination region of carriers - window layer (however, 0<1-X
≦0.5), and at least nitrogen atoms are added ()aAs 1-xPx
Composition - The window layer has an n-type impurity concentration gradual decreasing layer that gradually reduces the n-type impurity concentration in the initial stage when the n-type impurity concentration in the epitaxial film is changed from a high concentration to a desired low concentration. epitaxial wafer. 2. The n-type impurity concentration gradually decreasing layer is characterized in that the n-type impurity concentration gradually decreasing layer is provided with an epitaxial layer in which the n-type impurity concentration a is constant at least -j- or more. epitaxial wafer. 3. Composition of GaASl-xPX doped with nitrogen atoms - The window layer is at least one layer in a gradually increasing nitrogen concentration layer or a gradually increasing nitrogen concentration 71D layer in which the nitrogen concentration is gradually increased from 0 to a desired value. Claim 1 or 2, characterized in that it consists of a gradually increasing nitrogen concentration layer having an epitaxial layer with a constant nitrogen concentration and a nitrogen concentration window layer in which the nitrogen concentration is fixed at a desired value. Epitaxial wafer described. 4. The epitaxial wafer according to claim 1 or 2, wherein the single crystal substrate is gallium phosphide (GaP).