JPH07249582A - Crystal growth method - Google Patents

Abstract

PURPOSE:To prevent the reduction in the yield of an element and to increase the light emission efficiency by increasing a mol ratio of V group element and III group element in a gas flowing into a crystal growth oven for a part directly related to emission of light and decreasing the mol ratio for the other parts when growing AlGaInP crystal. CONSTITUTION:When performing epitaxial growth of AlGaInP solid solution crystal onto GaAsP substrate crystal from gaseous phase, the mol ratio between phosphine which is V group feed gas which becomes the raw material and an organic metal compound which is III group raw material is set to 300 or larger. For example, Ga (0.7) In (0.3) P crystal is allowed to grow by 2mu on the GaAsP substrate crystal at 700 deg.C with organic metal trimethylaluminum, triethylgallium, trimethylindium, and phosphine as raw materials. The curve of the photoluminescence intensity of the crystal versus V/III growth indicates that the photoluminescence intensity increases along with V/III and begins to converge from approximately 300.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a compound semiconductor device.

[0002]

2. Description of the Related Art AlGaInP type solid solution crystals are widely used as light emitting devices in the visible region. These elements are formed of a crystal having a composition Ga (0.5) In (0.5) P that is substantially lattice-matched with GaAs as a substrate crystal and a composition in which a part of this Ga is replaced with Al.

To make the emission wavelength shorter, Al or Ga is used.
It is necessary to increase the ratio of In and decrease In to increase the forbidden band width, but then the lattice constant of the crystal becomes smaller than that of GaAs which is the substrate crystal, and the lattice matching condition is largely deviated. In such a case, good quality crystals cannot be obtained. Therefore, it is necessary to use a crystal having a smaller lattice constant than GaAs for the substrate crystal.

One of them is GaAsP crystal.
In this method, GaAs is first epitaxially grown on a GaAs crystal, and then a GaAsP layer containing P is attached. At this time, the P composition is gradually increased. In this way, a composition graded layer is formed in which the lattice constant of the growth layer gradually decreases according to the P content. This layer has a function of relaxing lattice strain and reducing the density of dislocations caused by lattice mismatch, which is useful for improving crystallinity. The content of P is increased to a composition having a desired lattice constant, and thereafter, GaAsP having a constant composition is fixed to the composition.
Add layers.

Thus obtained, for example, GaA
For a GaAsP substrate crystal of s (0.6) P (0.4), Ga (0.7) In (0.3) P or (Al, Ga) InP in which a part of this Ga is replaced by Al Can be epitaxially grown in a lattice-matched state. In this description, the method of making a GaAsP substrate crystal starting from GaAs was described, but it is also possible to obtain a GaAsP substrate crystal by starting from GaP on top of GaP and gradually increasing the As content. AlGaI almost lattice-matched as described above on the substrate crystal thus obtained
Although an nP-based crystal is grown, it is desired that this layer has good crystallinity.

[0006]

When growing an AlGaInP type crystal, a metal organic vapor phase epitaxial growth method is usually used. One of the important variables in this growth method is the so-called V / III ratio, that is, the molar ratio between the group V element and the group III element in the gas flowing into the crystal growth furnace. This value affects the properties of the crystal. In the case of the AlGaInP / GaAsP system, which is a problem here, the luminous efficiency and the morphology change depending on V / III, but the directions are opposite to each other. That is, it has been found that it is necessary to increase V / III in order to increase the luminous efficiency, but on the other hand, the growth hills are significantly developed, and the yield of the device is reduced due to the deterioration of morphology. Therefore, it was necessary to control these contradictory phenomena.

[0007]

Since the growth hill develops as the thickness of the crystal layer increases, its influence is small if the growth layer is thin. Therefore, only the portion directly related to light emission grows at high V / III, and the other portion grows at low V / III.
It turns out that it is good to grow in III. This region is homo p
In the n-junction, this corresponds to the diffusion length of the injected minority carriers, and in the double heterojunction, this corresponds to the active layer sandwiched by the cladding layers.

[0008]

It is considered that at a high V / III, defects related to the group V atom in the crystal, that is, P, are reduced, and therefore the luminous efficiency is increased. On the other hand, it is not clear at present why the growth hills tend to develop when V / III is high and the crystal plane becomes flat when V / III is low, and it is necessary to wait for the clarification of the crystal growth mechanism.

[0009]

【Example】

(Example 1) A Ga (0.7) In (0.3) P crystal was grown to a thickness of 2 μ on a GaAsP substrate crystal at 700 ° C. using organometallic trimethylaluminum, triethylgallium, trimethylindium, and phosphine as raw materials. The photoluminescence intensity of this crystal is determined by the V
When plotted against / III, the result is shown in Fig. 1. As is clear from this, the photoluminescence intensity is V / II.
It increases with I and begins to converge around 300.
Therefore, from the viewpoint of only the photoluminescence intensity, it is sufficient to grow the crystal with V / III of 300 or more. However, from around this point, the growth hills started to be conspicuous, and when V / III was 900, it reached about 2000 / cm ² .

(Embodiment 2) As in the above embodiment, Ga
Al (0.5) Ga (0.2) In on AsP substrate crystal
(0.3) P / Ga (0.7) In (0.3) P / Al
A double heterojunction having a structure of (0.5) Ga (0.2) In (0.3) P is formed. The thickness of each layer is 1μ,
It is 0.5μ and 1μ. When growing these crystal layers, V / III was kept constant at 200, and V / III was V / III only when growing the middle light emitting layer Ga (0.7) In (0.3) P.
Comparing the photoluminescence intensities of III to 900, it was found that the latter showed a value five times higher. The density of growth hills is about 300 pieces / cm ^{2 for} all crystals.
And a low value. On the other hand, all crystal layers are V / II
When I was grown at 400, the density of growth hills was 1000 / cm ² , and the photoluminescence intensity remained in the middle of the above two kinds of crystals.

(Embodiment 3) The light emitting layer Ga (0.7) is formed by doping Zn and Si into two AlGaInP layers, which are clad layers in a double heterojunction, respectively.
A pn junction can be formed by sandwiching In (0.3) P. Light-emitting diodes are obtained by attaching ohmic electrodes to the p-side and the n-side of the wafer and then cutting the wafer into chips of 3 mm square. A light emitting diode in which only the light emitting layer was grown at V / III of 900 shows a light emission three times stronger than that of a light emitting diode made at V / III of 200.

In the above embodiments, GaInP is used as the light emitting layer.
Although the case of using a crystal has been described, the same relationship holds for an AlGaInP crystal in which a part of Ga atoms is replaced with Al.

[0013]

According to the present invention, when an AlGaInP-based crystal is grown on a GaAsP substrate, a crystal in which only the light emitting layer is grown at a high V / III and the other portions are grown at a low V / III is always maintained. It exhibits higher emission intensity than a crystal grown at high V / III or low V / III.

[Brief description of drawings]

FIG. 1 II for group V elements in the supply gas during crystal growth
Molar ratio of Group I elements and Ga (0.7) In at room temperature
The measurement figure which shows the relationship of the photoluminescence intensity of (0.3) P.

Claims (2)

[Claims] 1. When a AlGaInP solid solution crystal is epitaxially grown from a vapor phase on a GaAsP substrate crystal, phosphine which is a group V source gas and III
A crystal growth method, characterized in that the molar ratio of the organometallic compound as a raw material of the group is set to 300 or more. 2. The crystal growth method according to claim 1, wherein only the active region where electrons and holes are recombined and the vicinity thereof are grown at the above molar ratio.