JPS5946096B2 - Liquid phase epitaxial growth equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid phase epitaxial growth apparatus, and particularly to a growth apparatus suitable for epitaxial growth of a multicomponent semiconductor having easily evaporable component elements.

Liquid phase epitaxial growth is well known for use during the fabrication process of semiconductor lasers using multi-element semiconductors such as gallium arsenide (GaAs), gallium-aluminum-arsenic (GaAlAs), etc. as constituent materials.

Recently, it has also been adopted in the production of infrared detection elements, laser elements, etc. made of narrow energy gap semiconductors made of three elements: mercury (Hg), cadmium (Cd), and tellurium (Te). A semiconductor having two or three types of component elements described above is different from a true stoichiometric compound and has properties somewhat similar to a mixture (alloy).

Therefore, in this specification, such a semiconductor will be referred to as a multi-component semiconductor. A semiconductor composed of the three elements Hg and Cd2Te is generally represented by the composition formula Hgl-xCdxTe.

When liquid phase epitaxial growth (hereinafter simply referred to as liquid phase growth) is performed on this semiconductor, Hg in the component elements is extremely easily evaporated, so a large amount of Hg evaporates from the liquid phase, resulting in loss. There is a problem that the phase composition changes. In other words, liquid phase growth is generally carried out in an open tube, and hydrogen gas (H2) is constantly flowing inside the tube, so Hg in the liquid phase evaporates one by one and flows out of the tube together with H2, gradually leaving the liquid phase. It's getting lost. Therefore, H in the liquid phase
This leads to a considerable decrease in the amount of g. If liquid phase growth is performed in such a state, there is a disadvantage that only a grown layer having a composition lower in Hg content than the expected composition can be obtained. Furthermore, a method is already well known in which the multi-component semiconductor is sealed together with the component elements in a closed container in order to prevent evaporation of the easily evaporable component elements when heat-treating the multi-component semiconductor.

However, if liquid phase growth is attempted to be performed in a closed container, there are disadvantages such as the operation of bringing the growth substrate into contact with the liquid phase is troublesome, and multilayer growth is virtually impossible. The present invention has been made in view of the above-mentioned problems, and includes installing a device used for liquid phase growth in an open tube, placing an evaporation source for an easily evaporable component element in the tube, and at least one side of the device for liquid phase growth. It is an object of the present invention to provide a novel liquid phase epitaxial growth apparatus which makes it possible to create a state quasi-equilibrium between the liquid phase and the gas phase by providing a high temperature barrier.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a liquid phase epitaxial apparatus according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of an embodiment of the liquid phase epitaxial growth apparatus according to the present invention, in which a substrate holder 2 and a liquid phase storage section 4 are installed inside a core tube 1 made of quartz. The growth apparatus is essentially the same as a conventionally known growth apparatus in that a slider 3 having a slider 3 is installed, and a liquid phase melt 5 is housed in a liquid phase storage section 4. However, in addition to the crystal growth substrate 6, the substrate holder also contains Cd as a Cd source.
A Te thin plate 7 is held, and the melt 5 is once made of CdTe.
It is carried onto a thin plate 7 to melt the CdTe, and then transferred to a crystal growth substrate 6 (hereinafter referred to as the substrate), on which an epitaxial growth layer of Hgl-XCdxTe is grown. 8 is the substrate 6 and C until just before the start of crystal growth.
This is a protective plate that covers the surface of the dTe thin plate 7 to prevent Hg from evaporating from the surface.

In addition, in order to prevent Hg evaporation from the surface of the molten material 5,
A liquid level shielding plate 9 is installed above the liquid phase storage section 4 .
However, this structure of the growth device A has already been proposed by the present inventors, and is not the essence of the present invention.
Further, a push rod 10 for moving the slider 3 and a handle 11 of the substrate holder 2 are attached to the growth instrument A, and both of these extend outside the tube.

Next, in addition to the above-mentioned growth device A, an Hg source B is installed inside the furnace tube 1. The Hg source B has a small amount of metal Hgl3 contained in a container 12 with an open top, and is provided to establish a liquid-vapor phase equilibrium of Hg in the reactor core tube, as will be described later. Furthermore, as an important feature of the present invention, two high-temperature blocks C and D are installed at two locations within the reactor core tube.
is provided. In this embodiment, the high-temperature blocks C and D are carbon blocks having through holes, and are maintained at the highest temperature within the reactor core tube 1. The high-temperature block C has a small-diameter through-hole h in part, and H2 introduced from the gas inlet 1a flows into the furnace tube 1 through the through-hole h during the growth process. Also, push rod 10
The handle 11 of the substrate holder and the handle 14 of the Hg source pass through another high-temperature block D and come out of the reactor core tube 1, but the space between the high-temperature block D and the push rod etc. is not airtight; Rather, a slight gap is intentionally provided so that H2 can exit to the back side of the hot block D through this gap.

One end of the furnace tube 1 (on the right side in the figure) is sealed with a lid 15, and a push rod 10, a handle 11 of the substrate holder, and Hg
The source handle 14 hermetically passes through the lid 15 and is drawn out of the tube, and the H2 that has passed through the high temperature block D is discharged from the gas outlet 1b provided near the end of the core tube 1. .
Hereinafter, for convenience, high-temperature program C will be referred to as the first high-temperature program, and D will be referred to as the second high-temperature program. The four systems of heaters Ha, Hb, Hc, and Hd are for maintaining the area of the reactor core tube immediately below each at a predetermined temperature.

FIG. 2 is a graph schematically showing the temperature distribution inside the reactor core tube 1. The areas of both the first and second high-temperature blocks C and D have the highest temperature, followed by the area of the crystal growth device A. , the site of Hg source B is the coldest. The actual temperature is, for example, about 700'C for the high temperature process part, about 500'C for the crystal growth equipment part, and about 100'C for the Hg source part.
As is clear from the above description, in the furnace tube 1, the crystal growth device A and the Hg source B are installed in the space sandwiched between the first high temperature block C and the second high temperature block D.

Hg vapor evaporated from Hg source B is transferred to the first high temperature process C.
The second high-temperature block D suppresses the sending of instructions to the outside of both high-temperature blocks. The reason for this will be explained below. The first reason is that the space through which Hg vapor leaks is narrowly constricted.

The second reason is that the Hg vapor that has flowed into the gap between both high-temperature blocks and the reactor core tube 1 is heated and becomes diluted.
This is because the number of Hg atoms passing per unit cross-sectional area time decreases. As mentioned above, both high temperature processes C and D
As a result of suppressing the transport of Hg atoms to the outside, if the area of Hg source B is sufficiently large, the number of Hg atoms evaporated from Hg source B will be sufficiently larger than the number of Hg atoms lost to the outside of both high temperature processes C and D. be able to.

Therefore, the partial pressure of Hg vapor between the two high-temperature blocks is always approximately equal to the Hg vapor pressure of Hg source B at any point.
Therefore, if the temperature of the Hg source B is adjusted so that the vapor pressure is equal to the Hg vapor pressure from the liquid phase 5, the number of Hg atoms evaporated from the liquid phase 5 and the number of Hg atoms entering the liquid phase 5 from the atmosphere will be Hg
The number of atoms becomes equal, so the Hg content of the liquid phase 5 no longer decreases.

In the embodiment, the high-temperature blocks C and D are heated from the outside by a heater, but the blocks may be made of a heat-resistant insulator such as quartz, and the heater may be embedded inside. Further, the gas inlet 1a may be provided on the side surface of the reactor core tube inside the first high temperature block C (closer to the Hg source B).
The material of the growth substrate 6 is not necessarily Hgl-0Cdx.
It is not necessary to use Te; instead, CdTe, which can easily produce a large-area single crystal, may be used.

As liquid phase materials, Hg, Cd, and Te are used as metals (
It may be used by mixing and melting it in a single state, but it may also be used by melting HgTe, which is a binary alloy. In this case, Cd is supplied from the CdTe thin plate 7. Or again Hg
A liquid phase may be obtained by melting Te and CdTe in a mixed state. Based on its structure, the epitaxial growth apparatus according to the present invention allows for easy substrate replacement, multilayer growth, replenishment of raw materials, etc. in the same way as conventional open-tube type apparatuses; It has the excellent advantage of keeping evaporation to a minimum. Therefore, it is highly effective when used in the liquid phase epitaxial method of multi-component semiconductors containing easily vaporizable elements such as Hg, arsenic, and phosphorus.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of an embodiment of an epitaxial growth apparatus according to the present invention, and FIG. 2 is a graph showing the temperature distribution within the reactor core tube in FIG. 1... Furnace tube, 2... Substrate holder, 3
...Slider, 4 ...Liquid phase storage section, 5
...Liquid phase, 6...Substrate, 7...
・CdTe thin plate, 8...Protection plate, 9...
・Liquid level shielding plate, 13...Hg. A...
Crystal growth equipment, B... Hg source, C...
・First high temperature program, D...Second high temperature program.

Claims (1)

[Scope of Claims] 1. A liquid phase epitaxial growth apparatus and a source of vapor of easily evaporable components in a multi-component semiconductor to be grown are installed in a heat-resistant container having a gas inlet and a gas outlet, and the above-mentioned A high-temperature block having a through hole is attached between the epitaxial growth equipment and the gas exhaust port, and the gas in the container is discharged to the outside from the gas exhaust port through the through hole. Liquid phase epitaxial growth equipment. 2 A device for liquid phase epitaxial growth and a source of easily evaporable component vapor are arranged between a pair of high-temperature blocks, and gas is introduced into the container through a small-diameter through hole provided in one of the high-temperature blocks. A liquid phase epitaxial growth apparatus according to claim 1, characterized in that: