JPH0851234A - Method for growing semiconductor thin film - Google Patents

Abstract

(57) [Abstract] [Purpose] AlGaInP grown on GaAs substrate
Hillocks on the surface of the film are reduced to obtain a high brightness green light emitting device. [Structure] AlGaI on a GaAs substrate, which is lattice-matched with the GaAs substrate and exhibits a green emission color in photoluminescence or electroluminescence.
When a semiconductor thin film made of nP is epitaxially grown by the metal organic chemical vapor deposition method, the growth temperature is set to Tg ° C. and the supply ratio V / III of the group V source and the group III source is set to R.
When expressed as, the following three conditional expressions: 15 × Tg −1060
0 ≦ R ≦ 12.5 × Tg-8200, 680 ≦ Tg ≦ 7
The semiconductor thin film is grown at a growth temperature Tg and a V / III ratio R satisfying all of 40 and 200≤R≤800. [Effect] A growth film having a mirror surface and less hillocks can be obtained, and a high brightness green light emitting device can be obtained. The stoichiometric composition of the grown film at the substrate interface can be controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a semiconductor thin film in manufacturing a light emitting device such as a light emitting diode or a laser diode, and particularly to AlG on a GaAs substrate.
The semiconductor thin film of aInP is formed by metal organic chemical vapor deposition (MOCV).
The present invention relates to a technique effective when growing by the D method).

[0002]

2. Description of the Related Art (Al _x Ga _1-x ) _0.5 In _0.5 P (x
The semiconductor made of <0.7) has a forbidden band width corresponding to the emission wavelength of 540 to 660 nm and is a direct transition type.
D) and semiconductor laser diodes replacing He-Ne lasers are being applied. In particular, when the Al composition x is about 0.5, the forbidden band width corresponds to the green wavelength, so that the double barrier layer type high brightness green light emitting diode using the AlGaInP layer as an active layer. Used as a light emitting layer.

Such an AlGaInP semiconductor thin film is generally epitaxially grown on a GaAs substrate by MOCVD.

[0004]

However, the AlG
In the aInP film, particularly when the Al composition is large, a problem that many small projections called hillocks, which is a kind of defect that causes a decrease in light emission efficiency of a light emitting element, are likely to occur on the surface of the film. There was a point.

The present invention has been made in order to solve the above problems, and its purpose is to use GaA by MOCVD.
It is an object of the present invention to provide a method for growing a semiconductor thin film, by which hillocks on the surface of an AlGaInP film grown on an s substrate are reduced, and thus a high brightness green light emitting device can be obtained.

[0006]

In order to achieve the above-mentioned object, the present inventor has used a horizontal organometallic vapor phase epitaxy apparatus,
GaA with the (100) plane as the substrate surface in the growth apparatus
s substrate is installed, and triethylgallium (TEG) and trimethylindium (TM) are used as raw material gases.
I), trimethylaluminum (TMA) and phosphine (PH ₃ ) are flown, and AlGaIn of about 1 μm thickness is formed on a GaAs substrate under different growth conditions described below.
An experiment for epitaxially growing a P film was conducted.

(Experiment 1) First, the growth temperature Tg is set to 680.
The temperature range was changed to include 740 ° C. As a result, if the growth temperature Tg is set to a temperature within the range of 680 to 740 ° C,
It was found that the surface of the grown film became a mirror surface. Growth temperature T
When g was more than 740 ° C, the film surface became cloudy, while when it was less than 680 ° C, the surface became rough. The growth temperature Tg is a value obtained by measuring the carbon susceptor in the reaction tube with a thermocouple.

(Experiment 2) Next, with a group V raw material (PH ₃ ),
The supply ratio V / III with the group III raw materials (TEG, TMI, and TMA) was changed within a range including 200 to 800. As a result, it was found that when the V / III ratio was made too large, the surface of the growth film became rough, while when it was made too small, it became cloudy, but its criticality depends on the growth temperature Tg. That is, the value of V / III ratio suitable for obtaining a mirror surface is 2
It tends to increase within the range of 00 to 800 and as the growth temperature Tg increases.

(Discussion) When the surface of the grown film was observed with an optical microscope for each of the samples obtained in Experiments 1 and 2, even if the surface was a mirror surface, the growth temperature Tg was 680.
V / III ratio is relatively large in the range of ~ 720 ° C,
And V / II when the growth temperature Tg is in the range of 720 to 740 ° C.
A large number of hillocks occurred in the one with a relatively small I ratio. In summary, it was found that the growth condition where the surface of the growth film was a mirror surface and the generation of hillocks was small was the inside region of the polygon ABCDEF shown in FIG. In the film grown under the conditions in this region, the number of hillocks was reduced to about 1000 / cm ² , but outside the region, it increased to about 30,000 / cm ² or on the surface. Has become cloudy. When the lattice mismatch of each of the samples obtained in Experiments 1 and 2 was examined by XRD (X-ray diffractometer), both were 0.1% or less, and the photoluminescence was measured. ,
It was confirmed that the sample having a small number of hillocks emitted light having a peak at about 560 nm, and was suitable as a green light emitting device.

The present invention has been made on the basis of the above findings, and a semiconductor thin film made of AlGaInP on a GaAs substrate, which lattice-matches with the GaAs substrate and exhibits a green emission color in photoluminescence or electroluminescence. In the epitaxial growth by the metalorganic vapor phase epitaxy method, the growth temperature was set to Tg ° C, and V
When the supply ratio V / III of the group III raw material to the group III raw material is represented by R, the following three conditional expressions: 15 × Tg −10600 ≦ R ≦ 12.5 × Tg −8200 (1) 680 ≦ Tg ≦ 740 (2) 200 ≦ R ≦ 800 (3) Growth temperature Tg and V / III ratio R
Therefore, the semiconductor thin film is grown. In the present invention, preferably the growth temperature Tg
Is a temperature satisfying the following conditional expression: 690 ≦ Tg ≦ 730 (4), and more preferably, V / II
I ratio R is a value that satisfies the following conditional expression: 250 ≦ R ≦ 450 (5).

[0011]

The AlGaInP film is formed on the GaAs substrate under the growth conditions satisfying the conditions (1), (2) and (3) above.
By epitaxially growing the film, a growth film having a mirror surface and less hillocks can be obtained. Further, by satisfying the conditional expressions (4) and (5), the number of hillocks is further reduced. Therefore, a high brightness green light emitting element can be obtained.

It is considered that hillocks are generated due to the deviation of the stoichiometric composition of the growth film at the substrate interface. Therefore, according to the present invention, by defining the growth conditions as described above, the hillocks at the substrate interface are increased. The stoichiometric composition of the grown film will be controlled.

[0013]

EXAMPLES Examples of the method for growing a semiconductor thin film according to the present invention will be described below. The method of growing a semiconductor thin film according to the present invention is a method of growing Al on a GaAs substrate by MOCVD.
When the GaInP film is epitaxially grown, the growth temperature is Tg ° C. and the supply ratio of the group V raw material (PH ₃ ) to the group III raw material (TEG, TMI and TMA) is V / II.
I ratio R and the inside of the polygon ABCDEF shown in FIG. 1, that is, the following three conditional expressions: 15 × Tg −10600 ≦ R ≦ 12.5 × Tg −8200 (1) 680 ≤Tg ≤740 (2) 200 ≤R≤800 (3) The vapor phase growth is selected from an arbitrary combination within the range. Other growth conditions are the same as before.

AlG obtained under the above growth conditions
The aInP film lattice-matches with the GaAs substrate and
It is a semiconductor film whose emission color in photoluminescence or electroluminescence is green.

Here, the growth conditions are (1), (2),
It deviates from each conditional expression of (3), that is, the polygon AB in FIG.
The surface condition of the growth film is as follows, except for the inside region of the CDEF. That is, the surface condition is A- in FIG.
It becomes rough in the area above the B line (R> 800),
In the area on the right side of the AF line (Tg> 740), it becomes cloudy, and in the area below the line D-E (R <200), it becomes cloudy and many hillocks are generated.
In the area on the left side of the -D line (Tg <680), a large number of hillocks are generated in addition to being rough, and BC
Upper left area of the line (R> 12.5 × Tg-8200) and lower right area of the EF line (R <15 × Tg-10600)
If so, many hillocks will occur.

Next, three specific examples will be given to further clarify the features of the present invention, but the present invention is not limited to the specific examples.

In the following three specific examples, GaA having a (100) plane as a substrate surface is provided in a horizontal type metalorganic vapor phase epitaxy apparatus.
s substrate is installed, triethylgallium, trimethylindium, trimethylaluminum and phosphine are flown into the device, the combination of growth temperature Tg and V / III ratio R is changed, and Al of about 1 μm thickness is formed on the GaAs substrate.
A GaInP film was epitaxially grown.

The combination of the growth temperature Tg and the V / III ratio R is Tg = 720 and R = 400 (point K in FIG. 1) in Example 1, and Tg = 700 and R = 400 in Example 2 (see FIG. 1).
Point L), and in Example 3 Tg = 700 and R = 300 (point M in FIG. 1). Here, the V / III ratio R is defined as the group V raw material (PH ₃ ) and the group III raw material (TEG, TMI and T).
MA). In the specific example 1, TEG, TMI
And TMA supply amount is 0.18, 0.25,
It is 0.05 sccm, the supply amount of PH ₃ is 192 sccm, the specific example 2 is the same as the specific example 1, the specific example 3 is the same as the specific example 1 except that the supply amount of PH ₃ is changed to 144 sccm. there were. For other growth conditions,
The pressure in the reaction tube was 30 Torr, and the total flow rate of gas including hydrogen gas was 8 l / min.

Observation of each of the samples obtained in the above three specific examples showed that the surface of the grown film was a mirror surface, and the amount of hillocks generated was reduced to about 1000 pieces / cm ² , which is good. It was As a result of XRD, the lattice mismatch was 0.1% or less in all cases. Further, when the photoluminescence was measured, emission having a peak at about 560 nm was confirmed.

Therefore, as in the above embodiment, GaAs
When a light-emitting layer made of AlGaInP is epitaxially grown on a substrate to manufacture a light-emitting element, hillocks in the light-emitting layer are reduced and high-luminance green light emission can be obtained. Therefore, a high-luminance green light-emitting element should be manufactured. Is possible.

A vertical type vapor phase growth apparatus may be used instead of the horizontal type, and the surface of the GaAs substrate is (10
It is also possible to use one that is appropriately inclined in a specific direction from the (0) plane.

Further, it goes without saying that the combination of the growth temperature Tg and the V / III ratio R is not limited to the combination of the above-mentioned embodiments, and can be appropriately selected from the range defined by the present invention. If the combination is within the range, effects such as reduction of hillocks and green light emission can be obtained as in the above embodiment.

[0023]

According to the method for growing a semiconductor thin film of the present invention, an AlGaInP film is epitaxially grown on a GaAs substrate under the growth conditions that satisfy the above conditional expressions (1), (2) and (3). Therefore, a growth film having a mirror surface and less hillocks can be obtained. Further, by satisfying each of the conditional expressions (4) or (5), the number of hillocks can be further reduced, so that a high-brightness green light emitting device can be obtained. can get.

Further, the present invention has the effect that the stoichiometric composition of the growth film at the substrate interface can be controlled by defining the growth conditions as described above.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing defined ranges of a growth temperature Tg and a V / III ratio R in the present invention.

Claims (3)

[Claims] 1. An AlG on a GaAs substrate, which is lattice-matched with the GaAs substrate and exhibits a green emission color in photoluminescence or electroluminescence.
When the semiconductor thin film made of aInP is epitaxially grown by the metal organic chemical vapor deposition method, the growth temperature is set to Tg.
And the supply ratio V / III of the group V raw material and the group III raw material
Is expressed as R, the following three conditional expressions: 15 × Tg −10600 ≦ R ≦ 12.5 × Tg −8200 680 ≦ Tg ≦ 740 200 ≦ R ≦ 800 that satisfy the following growth temperatures Tg and V / III ratio R
Therefore, a method for growing a semiconductor thin film, which comprises growing the semiconductor thin film. 2. The method for growing a semiconductor thin film according to claim 1, wherein the growth temperature Tg is a temperature satisfying the following conditional expression: 690 ≦ Tg ≦ 730. 3. The method for growing a semiconductor thin film according to claim 1, wherein the V / III ratio R is a value satisfying the following conditional expression: 250 ≦ R ≦ 450.