JP3101753B2 - Vapor growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for vapor-phase growth of a compound semiconductor, and more particularly, to a substrate or layer made of a compound semiconductor containing As as a constituent element (hereinafter, "substrate or layer" is collectively referred to as "substrate etc." The present invention relates to a technique which is useful when applied to a case where an InGaP layer or an InGaAsP layer is epitaxially grown by a hydride vapor phase epitaxy method.

[0002]

2. Description of the Related Art A hydride vapor phase epitaxy method is one method for epitaxially growing a single crystal thin film of a compound semiconductor on a substrate or the like. This vapor phase growth method is widely used, for example, when growing a thin film having a mixed crystal composition on a III-V compound semiconductor substrate or the like because the growth rate is high and the controllability of the film thickness and composition is good. For example, it is often used to form a heterostructure epitaxial layer such as InGaP / GaAs in the production of an optical semiconductor device such as a semiconductor laser or a light emitting diode.

For example, when the above-mentioned InGaP / GaAs heterostructure is formed, a GaAs substrate or the like is placed in a reaction vessel of a vapor phase growth apparatus, and a Ga source gas, an In source gas, and a P source gas are placed in the reaction vessel. To cause an InGaP layer to grow epitaxially on a GaAs substrate or the like. G
The aAs substrate and the like are placed on the leeward side of the reaction vessel, and on the windward side, Ga alone and In alone as metal sources are placed in separate boats. Then, as shown in the time chart of FIG. 3, first, the P source gas P
H ₃ (phosphine) gas is supplied (time t ₀ ′). When the inside of the reaction vessel becomes a steady state (time t ₁ ′), HCl (hydrogen chloride) gas is further flowed into the reaction vessel to the above Ga simple substance and the above In simple substance, respectively.
HCl gas is brought into contact with n alone to generate a GaCl (gallium chloride) gas serving as a Ga source gas and an InCl (indium chloride) gas serving as an In source gas, respectively. The GaCl gas, the InCl gas, and the PH ₃ gas react with each other on the surface of a GaAs substrate or the like to generate InGaP. Since the P ₂ molecule generated from the PH ₃ gas reacts more easily with the GaCl gas than the InCl gas, the supply amount of the InCl gas to the substrate and the like is GaCl.
Control is performed so as to be 10 to 20 times the gas supply amount.

[0004]

However, like the above-mentioned heterostructure, an InGaP layer or an InGaP layer is formed on a substrate or a layer made of a compound semiconductor containing As as a constituent element.
When epitaxially growing a GaAsP layer, controllability such as the thickness of the grown layer and the mixed crystal composition may be poor.
That is, for example, when an InGaP layer is grown on a GaAs substrate, as shown in a schematic view of an enlarged photograph of a cross section of the growth layer shown in FIG. 4, irregularities occur at the interface (growth interface) between the GaAs substrate 1 and the InGaP layer 2. Not only is the interface not flat, but the thickness a ′ of the formed InGaP layer 2 is about 2 μm.
However, there is a problem that a thick epitaxial growth layer is not formed. Furthermore, the target mixed crystal composition of In _0.5 Ga _0.5 P (the ratio of GaP to InGaP is 50 at% and the lattice matching with the GaAs substrate is good) was not formed, and Ga became excessive. Composition, for example, In _0.1 Ga _0.9 P (Ga in InGaP)
The ratio of P is 90 at%. ) Is formed.

[0005] The above-mentioned problems are caused by the fact that the material of the substrate or the like is Ga
Not limited to As, InAs, GaAsP, In
The same applies to the case of a substrate or the like made of GaAs or InAsP.
The same applies to the case where a layer containing P as a constituent element, such as an AsP layer, is epitaxially grown.

The present invention has been made to solve the above problems, and an object of the present invention is to form an InGaP layer or an InGaAsP layer on a substrate or a layer made of a compound semiconductor containing As as a constituent element such as GaAs. In providing epitaxial growth of a layer by hydride vapor phase epitaxy, it is necessary to provide a vapor phase epitaxy method in which the thickness of the growth layer and the controllability of the mixed crystal composition are good and the interface between the substrate and the epitaxial growth layer is flat. is there.

[0007]

In order to solve the above problems, the present inventor has proposed that P and P be exposed to the surface of a substrate or the like before the start of epitaxial growth by using a PH ₃ gas previously supplied into a reaction vessel. Is replaced with As, or P fills a vacancy of As, so that GaP or Ga
AsP and the like are generated unevenly, which hinders the subsequent growth of the InGaP layer.
Since P is more reactive with Ga than In, a growth nucleus having a composition containing excessive Ga is generated on the surface of a substrate or the like at the start of epitaxial growth, and a layer having the same composition as the growth nucleus grows thereafter. I guessed it.

Then, the present inventor has proposed that the pH of the
Experiments were conducted with various introduction timings of the _three gases. As a result, the PH ₃ gas and the HCl gas were supplied substantially simultaneously into the reaction vessel so that the supply start timings of the PH ₃ gas, the GaCl gas, and the InCl gas to the substrate and the like were substantially the same. The interface with the layer was flat and good, but the thickness of the grown layer was as thin as about 5 μm, and its mixed crystal composition was In _0.15 Ga _0.85 P (InG
The ratio of GaP to aP is 85 at%. )Met. Further, HCl gas is first supplied into the reaction vessel, PH ₃ gas is supplied later, and GaCl gas and I
When the nCl gas was supplied before the PH ₃ gas, the interface between the substrate or the like and the epitaxial growth layer was flat and good, and the growth layer had a thickness of about 3
0 μm, and its mixed crystal composition is the target composition of In
_0.5 Ga _0.5 P.

The present invention has been made on the basis of the above-mentioned knowledge. In growing an InGaP layer or an InGaAsP layer epitaxially on a substrate or a layer made of a compound semiconductor containing As as a constituent element, the reaction vessel contains an InGaP layer or an InGaAsP layer.
The raw material gas and the Ga raw material gas are supplied before the P raw material gas, and after the inside of the reaction vessel has reached a steady state, the P
It is proposed to supply a source gas. Also,
The compound semiconductor containing As as a constituent element is GaAs.
s, InAs, GaAsP, InGaAs, or InA
sP.

[0010]

According to the above-mentioned means, GaCl gas and InC generated by the HCl gas previously supplied into the reaction vessel.
After the inside of the reaction vessel becomes steady state with
_{Since three} gases are supplied, GaCl molecules and InCl molecules are adsorbed on the surface of the substrate or the like placed in the container at the stage of starting the growth. Therefore, the P ₂ molecules generated from PH ₃ supplied later do not react with the substrate or the like, but react with the adsorbed GaCl molecules and InCl molecules.
Non-uniform formation of aP, GaAsP and the like is prevented, and the growth interface becomes flat.

The ratio of GaCl molecules to InCl molecules adsorbed on the surface of a substrate or the like depends on the reactivity between P ₂ molecules and GaCl molecules, the reactivity between P ₂ molecules and InCl molecules,
Gas and InC determined according to the size of
Since the ratio is substantially the same as the ratio according to the supply amount of the 1 gas to the substrate or the like, for example, one GaCl molecule corresponds to one InCl molecule.
It means that 0 to 20 pieces are adsorbed. That is, since GaCl molecules are surrounded by InCl molecules on the surface of the substrate or the like, GaCl molecules scattered on the surface of the substrate or the like substantially filled with the InCl molecules are used.
The P ₂ molecule does not selectively reach only the molecule and only GaP is not continuously generated, but GaP and InP are generated at a ratio of exactly 1: 1. Since the subsequent epitaxial layer grows with the growth nuclei as the growth nuclei, the GaP ratio is just 50 at.
%.

[0012]

The features of the present invention will now be described with reference to specific examples, comparative examples, and conventional examples. In the specific example, the comparative example, and the conventional example, an InGaP layer was epitaxially grown on a GaAs substrate by a hydride vapor phase epitaxy method.

(Specific Example) A GaAs single crystal substrate is placed in a reaction region in a reaction vessel of a growth apparatus, and the temperature of the substrate is raised to 650 ° C. while supplying hydrogen gas to the reaction region at a flow rate of 1000 ml / min. did. At the same time, two metal sources of In and Ga independently placed in the reaction
The temperature was raised to 0 ° C. After the temperatures are stabilized, HCl gas is supplied to the In and Ga metal sources at a flow rate of 30 ml / min and 5 ml / min, respectively, as shown in the time chart of FIG. Gas and In
InCl gas as a source gas was flowed into the respective reaction regions (time t ₀ ). This state was maintained for 30 minutes to bring the inside of the reaction vessel into a steady state, and then 30 ml of PH ₃ gas was supplied to the reaction area.
/ Minute (time t ₁ ), and the InGaP layer was epitaxially grown for 2 hours.

The composition of the obtained epitaxially grown layer has a target mixed crystal composition of In _0.5 Ga _0.5 P, that is, InG.
The ratio of GaP to aP is 50 at%, and G
The composition was lattice-matched to the aAs substrate. The growth interface between the GaAs substrate 1 and the InGaP layer 2 was flat as shown in the schematic diagram of the enlarged photograph of the cross section shown in FIG. Further, the thickness a of the InGaP layer 2 was about 30 μm.

(Comparative Example) Hydrogen gas was supplied to the reaction zone,
Heated substrate and two metal sources (In and Ga)
After the temperature is stabilized, HCl is added to each of these metal sources.
At the same time, the gas is supplied to flow the GaCl gas and the InCl gas to the respective reaction regions, and at the same time, the PH ₃ gas is also supplied.
The epitaxial growth of the aP layer was performed for 2 hours. The other conditions, such as the flow rate of each gas and the temperatures of the substrate and the metal source, were the same as in the above specific example. The composition of the obtained epitaxial growth layer was such that the ratio of GaP to InGaP was 85 at%. The growth interface was flat, and an InGaP layer having a thickness of about 5 μm was formed.

[0016] As in the time chart shown in (conventional example) Fig. 3, PH ₃ at the same time reaction zone supply start and hydrogen gas
Gas was supplied (time t ₀ ′). Then, after the temperatures of the heated substrate and the two metal sources (In and Ga) are stabilized, HCl gas is supplied to each of the metal sources, and the GaCl gas and the InCl gas flow into the reaction region, respectively (time t). ₁ '), the epitaxial growth of the InGaP layer was performed for 2 hours. The other conditions, such as the flow rate of each gas and the temperatures of the substrate and the metal source, were the same as in the above specific example. The composition of the obtained epitaxial growth layer is InG
The ratio of GaP to aP was 90 at%.
Also, as shown in the schematic diagram of the enlarged photograph of the cross section shown in FIG.
The growth interface between the GaAs substrate 1 and the InGaP layer 2 was not flat but was irregularly disturbed. Further, the thickness a ′ of the InGaP layer 2 was about 2 μm.

By comparing the above specific example with the comparative example and the conventional example, it is possible to supply the substrate in the reaction vessel with the InCl gas and the GaCl gas first and then supply the PH ₃ gas with a delay. It can be seen that it is extremely effective in improving the condition of the growth interface with the epitaxially grown layer, improving the controllability of the composition of the grown layer, and growing the layer thicker.

In the above embodiment, InGaP / GaAs is used.
The heterostructure of s has been described as an example, but the present invention is not limited to this. The same applies to the case where a compound semiconductor crystal containing P as a constituent element is epitaxially grown on a compound semiconductor crystal substrate containing As as a constituent element. Needless to say, the effect, that is, the controllability of the composition of the growth layer is good, and the effect that a thick growth layer is formed with a good growth interface can be obtained. For example, InAs, G
using aAsP, InGaAs, or InAsP,
The same effect can be obtained even when the InGaAsP layer is epitaxially grown. The same effect is naturally obtained not only in the case of epitaxial growth directly on the substrate but also in the case of epitaxial growth on a compound semiconductor layer made of GaAs, InAs, GaAsP, InGaAs or InAsP laminated on the substrate. It is.

Further, in the above embodiment, the case where the present invention is applied to a hydride vapor phase epitaxy method has been described as an example. However, it goes without saying that the present invention can be applied to other vapor phase epitaxy methods. Absent.

[0020]

According to the vapor phase growth method of the present invention, an In source gas and a Ga source gas are first supplied to a substrate or the like in a reaction vessel, and then a P source gas is supplied. At the start of the supply of the source gas, the surface of the substrate or the like is covered with the adsorption In and the adsorption Ga, and the P source gas reacts with the adsorption In and the adsorption Ga. This prevents non-uniform generation of GaP, GaAsP, etc. on the surface of the substrate or the like. Thereby, a flat growth interface is obtained and the epitaxial layer grows thick. In addition, the ratio of the In and Ga adsorbed on the surface of the substrate or the like depends on the supply amount of the In raw material gas and the Ga raw material gas to the substrate or the like (that is, In having low reactivity with P has high reactivity with In Ratio that is large enough to compensate for the low
Therefore, a growth nucleus in which the ratio of GaP to InP is exactly 1: 1 is generated on the surface of a substrate or the like, and thereafter an epitaxial layer having the same composition as the growth nucleus grows.
An epitaxial layer having a target composition in which the ratio of P is just 50 at% is obtained. Therefore, an InGaP layer or an InGaAs layer is formed on a compound semiconductor substrate or the like containing As as a constituent element.
The sP layer can be grown thick with good controllability of the composition ratio and good growth interface.

[Brief description of the drawings]

FIG. 1 is a time chart showing a supply timing of each source gas in a specific example to which a vapor phase growth method according to the present invention is applied.

FIG. 2 is a diagram schematically showing an enlarged photograph of a cross section of an epitaxial growth layer in the specific example.

FIG. 3 is a time chart showing a supply timing of each source gas in a conventional example given as a comparison.

FIG. 4 is a diagram schematically showing an enlarged photograph of a cross section of an epitaxial growth layer in the conventional example.

[Explanation of symbols]

Supply start time of t ₀ In source gas and Ga source gas t ₁ Start time of supply of P source gas 1 GaAs substrate (substrate made of compound semiconductor containing As as a constituent element) 2 InGaP layer

Claims (2)

(57) [Claims] An InGaP layer or an InGaP layer is formed on a substrate or a layer made of a compound semiconductor containing As as a constituent element.
The AsP layer Upon is epitaxially <br/> Le grown by hydride vapor phase epitaxy, an In source gas and Ga material gas into the reaction vessel was fed before the PH ₃ gas, the reaction vessel was a steady state after the vapor phase growth method characterized in that supplying PH ₃ gas into the reaction vessel. 2. The compound semiconductor containing As as a constituent element includes GaAs, InAs, GaAsP, and InGaAs.
2. The vapor phase growth method according to claim 1, wherein s or InAsP is used.