JPS59174597A - Vapor phase growing method of epitaxial film of gallium phospho-arsenide mixed crystal - Google Patents

Abstract

PURPOSE:To grow a film of a gallium phosphoarsenide mixed crystal, free from surface defects by temporarily lowering the temp. of a substrate of a gallium phosphide single crystal and suspending the feed of a gallium component in a stage for growing a gallium phosphide layer on the substrate. CONSTITUTION:A gallium phosphide layer is grown on a substrate of a gallium phosphide single crystal kept at 850-980 deg.C, preferably about 900-940 deg.C by feeding a posphorus component and a gallium component, and only the feed of the gallium componnt is supended. At the same time, the temp. of the substrate is lowered to 800-900 deg.C, preferably 820-850 deg.C. After the temp. becomes constant, the gallium component is fed again to grow a gallium phosphide layer. A layer of a gallium phosphoarsenide mixed crystal having a changing mixing ratio is then grown while gradually increasing the feed of an arsenic component such as AsH2, and a layer of a gallium phosphoarsenide mixed crystal having a constant mixing ratio is grown. Thus, an epitaxial film of a gallium phosphoarsenid mixed crystal suitable for use in the manufacture of a red or green light emitting diode is grown without causing surface defects.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for vapor phase growth of a gallium arsenide mixed crystal epitaxial film suitable for manufacturing orange to yellow light emitting diodes (LEDs).

Gallium phosphide arsenide mixed crystals can be used to manufacture so-called intermediate color light emitting diodes ranging from orange to yellow because the forbidden band width can be changed by changing the mixed crystal ratio. In this specification, the mixed crystal ratio represents the content of GaP, that is, X in the formula GaAs□-xPx.

Such a gallium arsenide phosphide mixed crystal epitaxial film usually includes a gallium nonatonide layer on a gallium phosphide single crystal substrate,
A so-called homoepitaxial layer is grown in a vapor phase, and then an As component such as AsH2 is introduced, and the amount of introduction is gradually increased to grow a gallium phosphide arsenide mixed crystal ratio change layer. After the mixed crystal content reaches a desired value, a layer with a constant mixed crystal content is grown.

However, in the conventional gallium arsenide mixed crystal epitaxial film grown by the above method, surface defects such as pyramids and hillocks occur on the surface, which causes a decrease in the yield of the epitaxial film. Ta.

The present inventors have arrived at the present invention as a result of extensive research aimed at preventing the occurrence of such surface defects.

The above object of the present invention is to provide a gallium arsenide phosphide layer comprising a gallium phosphide layer, a gallium arsenide phosphide mixed crystal content variable layer, and a gallium arsenide phosphide mixed crystal constant layer on a gallium phosphide single crystal substrate. In the method of vapor phase growing a mixed crystal epitaxial film, the step of growing the gallium phosphide layer is a first step of growing the gallium phosphide layer by setting the temperature of the single crystal substrate in the range of gso← to qgoc. , After the seventh step, the supply of only the gallium component among the thin component and the gallium component was cut off, and the temperature of the single crystal substrate was lowered to g00cm.
A method characterized by comprising a third step in which a gallium phosphide layer is further grown after the second step and the first step, in which the temperature is lowered to a temperature in the range of 900'l and lower than the temperature in the first step. I can't stand it.

The gallium phosphide single crystal substrate used in the present invention preferably has a plane inclined by 2 to g0 with respect to the (100) plane.

In addition, the gas composition for vapor phase growth is Ga-Hot-
PH3-AsH3 system, Ga (CH3)3- As H
, -PH, and the like are preferred.

In the first step, the temperature of the gallium phosphide single crystal substrate is set to gso'6-qgor), preferably 7θorb~q
It is appropriate to set the temperature to qoC. If the temperature of the substrate is high, the crystallinity of the epitaxial layer obtained will be good, but the growth rate of the epitaxial layer will be low, so the above temperature is appropriate.

The thickness of the gallium phosphide layer grown in the first step is /~S
The thickness is preferably about μm. After the first step, the substrate temperature is lowered to a temperature lower than the temperature in the first step. this is,
This is because the growth rate of the gallium phosphide layer is slow at high temperatures, so the substrate temperature is lowered to increase the growth rate and improve productivity. In this case, if the gallium phosphide layer is grown at the same time as the substrate temperature is lowered, the crystallinity of the gallium phosphide layer will deteriorate, so it is necessary to stop the growth. In order to prevent phosphorus from scattering, it is necessary to cut off only the supply of the gallium component of the phosphorus component and the gallium component.

The temperature of the substrate is goo'5-qooc, which is good.

After the temperature is maintained at a constant temperature in the range of gso-gsoC and lower than the temperature in the first step, a third step is performed in which the supply of gallium component is started and a gallium phosphide layer is grown.

The thickness of the gallium phosphide layer grown in the third step is usually about 1 to S μm.

After the third step is completed, a layer with a variable amount of gallium phosphide arsenide mixed crystal is grown while gradually increasing the supply amount of an arsenic component such as AsH3. This is to alleviate the strain caused by the difference in lattice constant between gallium phosphide and the gallium arsenide phosphide mixed crystal that constitutes the constant gallium phosphide mixed crystal layer, thereby preventing the occurrence of dislocations, etc. be. After the mixed crystal content reaches a desired value, a layer of constant mixed crystal content of gallium arsenide phosphide is grown.

In this case, if the mixed crystal ratio is greater than o or lIs, indirect transition occurs, so it is preferable to dope nitrogen as an isoelectronic trap in order to improve luminous efficiency.

The epitaxial wafer having the epitaxial film obtained by the method of the present invention is free from surface defects such as i-plane K hillocks and pyramids, and has high productivity, so it has great industrial value.

゛The present invention will be explained in more detail below based on Examples.

Example 1 Yellow (peak emission wave summary 3 g g nm±) according to the present invention
2Q nm) Gallium arsenide epitaxial film for light emitting diode, GaAel-xPX, ×4o, g
sλ was formed on a GaP single crystal substrate as follows.

First, sulfur (S) is added as an n-type impurity at 3 x 1015 atoms/cA, and the GaP single crystal has a crystallographic plane deviated by about 6° from the (10o) plane in the 〈/10〉 direction. A board was prepared. Initially, the GaP single crystal substrate was approximately 37
Although the thickness was 0 μm, mechanical-chemical polishing (Mechanical-Oh
30 by eaical polishing) treatment
The thickness was 0 μm.

Next, the polished GaP single crystal substrate and the high-purity Ga-containing quartz boat were set at predetermined locations in a horizontal quartz epitaxial reactor with an inner diameter of 70 rrnn and a length of 100 cm. Argon (Ar) was introduced into the epitaxial reactor to sufficiently replace and remove air, and then hydrogen gas (H2) was introduced as a carrier gas at a rate of 700 m/min.
0 cc was introduced, the flow of Ar was stopped, and the temperature raising process began.

The temperatures of the Ga-containing quartz port set region and the GaP single crystal substrate set region are g, ? After confirming that OJ: and 93 θC were maintained, vapor phase growth of an epitaxial film GaAs1-xPx for a yellow light emitting diode was started.

At the start of vapor phase growth, hydrogen sulfide (H2''), which is an n-type impurity, diluted with nitrogen gas at a concentration of 60 ppm per minute.
C was introduced, while high-purity hydrogen chloride gas (H
By introducing 10 cc of Cl) per minute and reacting with Ga, '! ″/θθ%, converted to GaC!t and generated,
On the other hand, PH3 with a concentration of 10 diluted with H2 is heated at λ61 per minute.
After introducing ICC, the first GaP epitaxial layer was formed on the Gap single crystal substrate while maintaining the growth temperature (corresponding to the substrate temperature) at 930 C for the first 70 minutes.

Hydrogen chloride (HCl), which is a source of Ga, was shut off, and only the growth temperature was lowered from 930C to ggoC without changing the flow rates of other gases.

After the temperature became constant at ggoC, hydrogen chloride (HCl, ), which is the source of 1yGa, was resupplied and the second Ga
A P epitaxial layer was formed on the first epitaxial layer.

For the next 60 minutes, the growth temperature was kept constant at gg'o'6 and AsH3 diluted with NH2 at a concentration of 10 was added every minute to OC.
The third GaABl-xPx epitaxial layer was gradually introduced at 36 cc 4 from C, and the third GaABl-xPx epitaxial layer was
was formed on the epitaxial layer.

For the next 30 minutes, without changing the flow rate of each gas, that is, H
2, H2S, HCt, PH3 and AsH3 at 3θθθcc, acc, /lθC per minute, respectively.
By introducing C, 21rg cc and 36cc, the Ga of the th
An As1-xPx epitaxial layer was grown.

Next, for the final 60 minutes, in addition to the conditions for forming the epitaxial layer in G.
CC was introduced and nitrogen (N) was doped as an isoelectronic trap.

A m j GaA 8 H-xPX epitaxial layer was formed, and the entire formation process of the epitaxial multilayer film was completed.

The surface condition of the epitaxial wafer after removal was extremely good, with no protrusions or other surface defects observed.

For the epitaxial multilayer film obtained as above,
As a result of various physical property measurements and analyses, the first. The layer thickness of each λ-th epitaxial layer is 2. g ttm
, 3. The composition was a variable composition layer of km, j, /9.2 μm and a constant composition layer of /0.31 Lm.

Also, the n-type carrier concentration is 1. In the epitaxial layer region of the λth, 3rd degree and the 3rd degree, approximately ? X/0”cm
-3, and 7J x 10 Cm in the S-th epitaxial layer region doped with nitrogen.

Next, a yellow light emitting diode was prepared using the epitaxial wafer having the epitaxial film obtained in this example, and its brightness value (light output) was actually measured.

That is, the epitaxial wafer was prepared using ZnAs2.2! as a p-type impurity. It was vacuum-sealed in a high-purity quartz ampoule together with ~, and impurity thermal diffusion was performed at a temperature of 72°C.

The resulting p-n junction depth was 99.38 m from the surface.

The epitaxial wafer obtained as above,
The product is put into a series of device production lines including backside (substrate) polishing process, electrode formation process, wire ↑ bonding process, etc.
A yellow light emitting diode chip was created.

Next, the light emitting diode chip (chip... size and p
/n junction (both dimensions are SOOμ × 50θμ angle), a current with a DC current density of 20A/cr/l is applied, and the brightness value (light output) is measured under the condition that the chip is not coated with epoxy resin. did.

As a result, the peak emission wavelength is k g g nm! inm
Brightness value has increased 00 Ft-L-! ;230 Ft-L,
average! It was r/30Ft-L.

Example U Using the same device as that used in Example 1, a gallium arsenide epitaxial film GaAs+-ShioMo; 0, A 5) for an orange light emitting diode based on the present invention was prepared using GaP.
Formed on a single crystal substrate.

That is, sulfur has 3.3 X 1017 atoms 7' ctr
About 50 l-doped in the 〈/10〉 direction from the (100) plane
An epitaxial film GaPe, -xPx was grown in a vapor phase on a shifted n-type GaP single crystal substrate.

First, from the start of vapor phase growth, H2S diluted with nitrogen gas to a concentration of 4 cc/min, H2 as a carrier gas at 30.00 cc/min, and group Ⅰ component GaC
HCl for 1 formation was introduced into the epitaxial reactor at t, occ, and PH3 at a concentration of 10% as a V group component at a rate of 95 CC1 per minute, respectively, and 5 growth regions (corresponding to the substrate temperature) were introduced into the epitaxial reactor. The first GaP epitaxial layer was formed by maintaining the temperature at 9300° C. for 70 minutes.

Next, the supply of hydrogen chloride (HCl), which is the source of Ga, was cut off, and other gases, namely H2, H2S, and PH3, were introduced at fixed amounts of 3000 cc, 6 cc, and 1/min, respectively. Growth temperature from q3oC to gs
It was lowered to oC.

Next, after the temperature became constant at gsoC, the supply of hydrogen chloride (HCl), which is a Ga supply source, was restarted and a second GaAB, -xPx epitaxial layer was formed for 70 minutes.

During the next 90 minutes, the growth temperature was kept constant at gsoC, and H2, H2S, HO7, and PH were added every minute to yooo cc, b cc, OCC, and /
q5 Keep a constant amount of QC, AsH2 only from OCC every minute / 0! ; Gradually increase to cc\
, a third GaAS, -xPx epitaxial layer was formed.

For the next 75 minutes, the growth temperature was held constant at gsoc;
Also H2, H2S, HOt, PH3 and AsF3
, respectively, 3000cc', bcc, OtsuQcc,
/9! ; While maintaining CC and /'03c, tc constant, NH3 was newly added at 230 cc/min, and the fifth G
An aABl-xPx epitaxial layer was formed to complete all epitaxial film formation steps. The surface condition of the epitaxial urethane after epitaxial growth was extremely good, with no protrusions or other surface defects observed.

The first. The layer thicknesses of the first and third epitaxial layers are z and b ttm, respectively.
, 3. '/ tlm, xll, 3 ttm, /
0.2 pm, and the S layer has nitrogen at 7×/θ19 cm−
3 was added, and the thickness was 3 μm.

Next, an orange light emitting diode was produced using the epitaxial film having the epitaxial film obtained in this example according to the method described in Example 1, and the luminance value was actually measured.

As a result, the light emitting diode chip obtained in this example (the tip dimensions and the p/n junction dimensions are both S
OOμ x 300μ square), DC current density/θA/f
When a current of fl is applied and the chip is not coated with epoxy resin, the brightness value is 2g3θFt -L~, 70A.
0Ft-L, and an average of 29gθFt-L, confirming that high brightness values were obtained in this example as well.

The peak emission wavelength was A 30 nm −1 m 2 nm.

Patent applicant Mitsubishi Monsanto Chemical Co., Ltd.
Mitsubishi Kasei Corporation procedural amendment (voluntary) 2 Name of the invention Method for vapor phase growth of gallium sino-arsenide mixed crystal epitaxial film 3 Relationship with the case of the person making the amendment Patent applicant 5 Subject of the amendment Description of the specification Contents of amendment in Column 6 of Detailed Description of the Invention (1) The second line of page 2 of the specification is corrected as follows.

(L, FiD) J (2) Lines 6 and 7 of page 2 of the specification are corrected as follows.

[The forbidden band width can be changed by changing the width of the forbidden band, so it is a so-called intermediate color light emitting diode that ranges from red to green.'' (3) Page 4, line 20 of the specification is corrected as follows.

``±2 nm'' January (
4) Correct line S on page 13 of the specification cylinder to the following text.

``For the next ttS minute, keep the growth temperature g5θ℃ constant.''
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Claims (1)

[Claims] A gallium phosphide arsenide mixed crystal epitaxial film including a gallium phosphide layer, a gallium phosphide arsenide mixed crystal ratio variable layer, and a gallium phosphide arsenide mixed crystal constant layer is grown in a vapor phase on a gallium phosphide single crystal substrate. In the method, the step of growing the gallium phosphide layer increases the temperature of the single crystal substrate to gs.
The first step is to grow a gallium phosphide layer in the range of oC-qgoC. After the first step, only the supply of the gallium component of the phosphorus component and the gallium component is cut off, and the temperature of the single crystal substrate is A method characterized by comprising a second step in which the temperature is lowered to a temperature within the range of -QOOC and lower than the temperature in the first step, and a third step in which a gallium phosphide layer is further grown after the first step.