JPH0139999B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the composition of a grown layer formed by liquid phase epitaxial growth and a method for growing a thick film.

Liquid phase epitaxial (hereinafter abbreviated as LPE)
When growing a compound containing aluminum (Al) using a growth method, Al dissolved in the solution
Since the amount of Al in the solution is very small and the distribution coefficient is very large, the Al concentration in the solution becomes insufficient near the growth layer, forcing the growth rate to slow down, or the Al concentration in the entire solution decreases rapidly. This limits the thickness of the grown layer.

Specifically, AlxGayIn ¹ −x−yAs on InP substrate
This will be explained by taking LPE growth of a quaternary compound as an example. InP
When the growth temperature is set to 700°C, taking into consideration that the difficulty of releasing P from the substrate increases above 700°C,
The mole fraction of Al in the growth solution for AlxGayIn ¹ −x−yAs remains at a maximum of X ^l _Al = 0.0002, and the Al concentration in the solution decreases rapidly due to LPE growth, and the thickness of the grown layer is about 0.4 μm. This is the limit. If the growth temperature is set to 800
Even if the temperature is raised to ℃ to increase the amount of Al dissolved,
The thickness of the growth layer is limited to about 1 μm. When the target is a light absorption layer of a semiconductor light receiving element, etc., this thickness is insufficient and a good light receiving element cannot be constructed.

In addition to the above example, in the LPE growth method, the mole fraction of the solution components gradually changes as the solid phase grows, and the composition of the grown layer also changes in accordance with the change in the solution components. In the conventional technology, the composition of the solution, the growth start temperature, the degree of supercooling, the cooling rate, the growth time, etc. are selected as a means of responding to changes in the composition of the growth layer. This is a very unsatisfactory method for obtaining a grown layer with the same composition and thickness.

The present invention aims to control the composition of a grown layer formed by LPE growth, and to obtain a grown layer having a desired composition and thickness.

The object of the present invention is to bring an electrode made of a substance containing at least one component of a solution into contact with the solution in an electroepitaxy method, and to introduce the component into the solution by an electric current passing through the solution between the substrate and the electrode. This is achieved by controlling the dissolution of, and thus the concentration of, the components in solution during epitaxial growth.

The present invention will be specifically described by way of examples with reference to the drawings. The figure is a schematic diagram showing an example of growing an AlxIn ¹ -xAs ternary compound on an InP substrate by the method of the present invention. In the figure, 1 is a fixed part of the boat, 2 is a slider of the boat, both of which are made of carbon, and 3 is a boron nitride.
= BN). The electrode 4 inserted into the fixed part 1 of the boat makes electrical contact with the fixed part 1 of the boat and is connected to the lead wire. Further, an InP substrate 5 is housed in a recess on the upper surface of the fixed part 1 of the boat.

When forming the LPE growth layer of the AlxIn ¹ -yAs ternary compound, the slider 2 is positioned at a position where the solution 6 contacts the InP substrate 5 as shown in the figure, and the solution 6 is an Al-As-In ternary solution.

In this example, as shown in the figure, solid phase Al
7 and InAs crystal 8 are placed on top of the solution 6 in contact with it, and lead wires 9 and 9' are connected independently to each other. Al7 in this example has a rod shape with a circular cross section, its side surface is wrapped in an alumina (Al ₂ O ₃ ) cylinder, and the surface in contact with the solution 6 is limited to its lower end surface, and furthermore, Al7 is in the solution 6. As the solution melts, the level of the solution inside the cylinder rises, constantly
The structure allows a certain area of Al7 to be in contact with the solution, making control easy and reliable.

The mixture of materials forming the solution before the start of LPE growth has a rejection ratio of In:InAs:Al=5.9695g:1.0g:0.00029g, and in addition, Al7, InAs crystal 8, and InP substrate 5 as described above are arranged. The entire apparatus shown in the figure is housed in a reaction tube, and the mixture is dissolved by raising the temperature while flowing pure hydrogen, and once it reaches 650°C, it is maintained at this temperature until the end of growth. 650℃
30 minutes after reaching , slide the slider 2 of the boat to introduce the solution 6 onto the InP substrate 5 and bring them into contact.

At the same time as the solution 6 is brought into contact with the InP substrate 5, the fixed part 1 side of the boat is turned positive (plus), Al7 and InAs
InP board 5 with 8 side as negative polarity.
-Solution 6-Al7 and InP substrate 5-Solution 6-InAs
A current is passed between 8 and 8. Al7 and InAs8 are electrically independent and it is possible to control the current value separately, and it is possible to control the current value of Al7 or InAs8 depending on the current value.
The rate of dissolution of InAs 8 into solution 6 is determined.

At the same time as melting Al7 or InAs8, InP substrate 5
An AlInAs crystal is electroepitatically grown thereon, and the composition of this AlInAs ternary growth layer can be controlled by the rate of dissolution of Al7 or InAs8 into the solution 6, ie, by the current flowing through each. In this example, the unit area of the InP substrate 5 is 20 A/cm ² on the InAs side and 0.1 A/cm ² on the Al side.
An approximately 2 μm thick Al ^0.5 In ^0.5 As grown layer was obtained by electroepitaxy growth for 1 minute.

In the electroepitaxy growth method according to the present invention as in the above-mentioned embodiments, it is possible to eliminate the temporal change in the concentration of solution components as in the conventional LPE growth method, and to make the composition of the grown layer uniform. As a result, it is also possible to obtain a grown layer with a thickness that could not be grown using conventional LPE growth methods.

Furthermore, by intentionally changing the current during electroepitaxy growth, the concentration of the solution components can be changed over time to give a change in the composition in the thickness direction of the grown layer, or if necessary, the concentration of the solution components can be changed over time. It is also possible to increase or decrease the number of elements constituting the solution and thus the growth layer by adding movement of the electrodes.

Further, in the above embodiments, the temperature during the growth layer formation was kept constant, but it is also possible to add temperature control similar to the conventional LPE growth method.

As explained above, the present invention uses an electroepitaxy method in which an electrode made of a substance containing at least one component of a solution is brought into contact with the solution, and a current is passed through the solution between the substrate and the electrode, thereby introducing the component into the solution. The dissolution and therefore the composition of the grown layer are controlled by the current, and it has a great effect on the formation of epitaxially grown layers, such as the formation of double heterostructures of compound semiconductors.

[Brief explanation of drawings]

The drawings are schematic diagrams showing embodiments of the present invention. In the figure, 1 is a fixed part of the boat, 2 is a slider of the boat, 3 is an insulating layer, 4 is an electrode, 5 is an InP substrate, 6 is a solution, 7 is Al, 8 is InAs, 9 and 9' are lead wires. show.

Claims (1)

[Claims] 1. In an epitaxial growth method in which a solution containing two or more elements is brought into contact with a substrate crystal surface to form a growth layer made of the component elements of the solution, an electrode made of a substance containing at least one of the component elements is brought into contact with the substrate crystal surface. An epitaxial growth method, characterized in that a current is passed through the solution between the substrate and the electrode, and the composition of the growth layer is controlled by the current.