JPS6316902B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid phase epitaxial growth method,
In particular, the present invention relates to a method for epitaxially growing a multi-component semiconductor layer containing an easily vaporizable component such as mercury.

For forming multi-component semiconductor layers such as mercury-cadmium-tellurium (HgCdTe) used in the production of infrared sensing elements, gallium-arsenic (GaAs), gallium-aluminum-arsenic (GaAlAs) used in the production of semiconductor lasers, etc. A liquid phase epitaxial growth method is used.

When performing this liquid phase epitaxial growth (hereinafter simply referred to as liquid phase growth), if the components of the multi-component semiconductor to be grown include extremely easily evaporated components such as Hg, a large amount of Hg evaporates from the liquid phase. and is lost, eventually changing the composition of the liquid phase. In other words, liquid phase growth is generally performed in an open tube, and hydrogen (H ₂ ) gas etc. is constantly flowing through the tube, so Hg in the liquid phase
is gradually evaporated and flows out of the tube along with H ₂ , and is gradually lost from the liquid phase. Therefore, the amount of Hg in the liquid phase gradually decreases. If liquid phase growth is performed under such conditions, only a grown layer with a composition lower in Hg content than the expected composition can be obtained.

In order to solve this problem, the inventors previously published Japanese Patent Application No. 55-80541 (Japanese Unexamined Patent Publication No. 57-5326).
A source of easily evaporable component vapor is provided in a position different from the growth zone in which the liquid phase growth equipment is installed in the open-tube reaction tube, and a carbon material slightly smaller than the inner diameter of the reaction tube is placed between the two. By arranging a block consisting of the above-mentioned two blocks, restricting the gas flow path to a small area, and making this block the highest temperature in the above-mentioned growth system, the region sandwiched between the above two blocks can be separated from the liquid phase and the gas phase. We have proposed a liquid phase epitaxial growth apparatus that can be used as a reaction space in which the phase is in a substantially equilibrium state (hereinafter referred to as a quasi-equilibrium state).

In the case where a multi-component semiconductor layer containing an easily evaporable component such as mercury (Hg) is grown among its constituent components by performing liquid phase growth in a reaction space in which a quasi-equilibrium state is created using the above invention. It has also become possible to precisely control the component composition.

However, on the surface of the growth layer grown in this manner, easily vaporizable components such as Hg and compounds of Hg and other elements precipitate and adhere. Therefore, the deposits had to be removed by polishing or the like after liquid phase growth. Such a problem generally occurs when the reaction space for liquid phase growth is made into a quasi-equilibrium system.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a quasi-equilibrium liquid phase epitaxial growth method that does not generate deposits on the surface of the grown layer. Therefore, the feature of the present invention is to make the reaction space a quasi-equilibrium system until the end of growth, and to form a supersaturated region in at least a part of the remaining area of the reaction space excluding the growth zone during the cooling period after the end of growth. There is a particular thing.

An example of growing a Hg _1-X Cd _X Te layer on a CdTe substrate will be described below as an embodiment of the liquid phase epitaxial growth method of the present invention.

FIG. 1 is a cross-sectional view of the main parts showing the structure of the liquid phase epitaxial apparatus used in the above embodiment, in which a substrate holder 2 is placed inside a core tube (reaction tube) 1 made of quartz.
A slider 3 having a liquid phase storage section 4 is installed, and the liquid phase storage section 4 houses a liquid phase melt 5, which is essentially the same as a conventionally well-known growth apparatus. . However, in addition to the substrate 6 for crystal growth, the substrate holder holds a CdTe thin plate 7 as a Cd source, and the melt 5 is once conveyed onto the CdTe thin plate 7 to dissolve the CdTe, and then the crystal grows. The substrate is transferred onto a CdTe substrate 6 (hereinafter referred to as the substrate), and an epitaxial growth layer of Hg _1-X Cd _X Te is grown on its surface. A protective plate 8 covers the surfaces of the substrate 6 and the CdTe thin plate 7 until just before the start of crystal growth to prevent Hg from evaporating from the surfaces.
Further, in order to prevent Hg from evaporating from the surface of the melt 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.

Push rod 1 for further moving slider 3
0 and the handle 11 of the substrate holder 2 are attached to the growth instrument A, and both 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 Hg 13 contained in a container 12 with an open top, and is provided to establish a liquid phase-vapor phase equilibrium of Hg in the reactor core tube, as will be described later.

Furthermore, two high temperature blocks C and D are provided at two locations within the reactor core tube. In this embodiment, both 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 H ₂ introduced from the gas inlet 1a flows into the furnace tube 1 through the through-hole h during the growth process.

In addition, the push rod 10, the handle 11 of the substrate holder,
The handle 14 of the Hg source passes through another high-temperature block D and comes out of the reactor core tube 1, but the space between the high-temperature block D and the push rod, etc. is not airtight, but rather there is a slight gap intentionally left. is provided so that H ₂ exits to the back side of the hot block D through this gap.
One end of the reactor core tube 1 (the right end in the figure) is sealed with a lid 15, and the push rod 10, the handle 11 of the substrate holder, and the handle 14 of the Hg source pass through the lid 15 in an airtight manner and are exposed to the outside of the tube. The high temperature block D
The H ₂ that has passed through is discharged from a gas outlet 1b provided near the end of the furnace tube 1. Hereinafter, for convenience, high-temperature block C will be referred to as the first high-temperature block, and D will be referred to as the second high-temperature block.
We will call it the high temperature block. 4 heaters
Ha, Hb, Hc, and Hd are used to maintain the area of the reactor core tube directly below each at a predetermined temperature.

Furthermore, a gas supply pipe 16 is provided outside the reactor core tube 1 for blowing out a cooling gas such as high pressure air or high pressure nitrogen (N ₂ ). The position may be any place other than the growth zone where the growth device A is installed in the reaction space between the high temperature blocks C and D. This gas supply pipe is provided to form a supersaturated region within the reaction space during the cooling period after the liquid phase growth is completed.

Next, using the above liquid phase epitaxial growth apparatus,
The process of growing the Hg _1-X Cd _X Te layer will be explained.

FIG. 2 is a graph schematically showing the temperature distribution during epitaxial layer growth as an example of the temperature distribution in the reactor core tube 1 until the end of liquid phase growth.
The parts of the second high-temperature blocks C and D have the highest temperature, followed by the part of the crystal growth device A, and the Hg
Source B sites are the coldest. The actual temperatures are, for example, approximately 700°C in the high temperature block area, approximately 500°C in the crystal growth device area, ie, the growth zone, and approximately 100°C in the Hg source area.

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 a space sandwiched between the first high temperature block C and the second high temperature block D. The Hg evaporated from the Hg source B is prevented from being transported outside the first high temperature block C and the second high temperature block D. 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 core tube 1 is heated and becomes diluted, and therefore the number of Hg atoms passing through a unit cross-sectional area in a unit time decreases. It is.

As mentioned above, the outside of both high temperature blocks C and D is
As a result of suppressing the transport of Hg atoms, if the area of Hg source B is sufficiently large, the number of Hg atoms evaporated from Hg source B can be made sufficiently larger than the number of Hg atoms lost to the outside of both high-temperature blocks C and D. . Therefore, the partial pressure of Hg vapor in the reaction space sandwiched between the two high-temperature blocks is always approximately equal to the Hg vapor pressure of Hg source B at any location. In other words, a quasi-equilibrium state appears in the reaction space.

Note that this example is an embodiment in which a first high temperature block C and a first high temperature block D are arranged, but the first high temperature block C is a block provided in the gas inflow direction, and the Hg vapor flows against the gas flow. is rarely transported, and therefore, it is sufficiently possible to bring about a quasi-equilibrium state with only the first high-temperature block D between the crystal growth device A and the gas outlet 1b.

Therefore, if the temperature of the Hg source B is adjusted so that the above 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 evaporated from the atmosphere into the liquid phase 5 will be reduced. The number of Hg atoms entering is equal to
The Hg content of liquid phase 5 no longer decreases. As a result, the Hg content in the grown layer does not decrease below the expected amount, and the component composition of the grown layer can be accurately controlled.

After completing the growth of the desired Hg _{1-X Cd} However, at this time, in this embodiment, high pressure air is blown out from the gas supply pipe 16 to locally rapidly cool the reactor core tube 1. As described above, the location is selected outside the growth zone in the reaction space.

In the rapidly cooled portion of the reactor core tube 1, the temperature inside the reactor core tube 1 also decreases, and the atmosphere in the reaction space becomes supersaturated with Hg and the like in this portion and its vicinity. Therefore, excess Hg vapor and the like contained in the atmosphere of the supersaturated region 17 is precipitated and adsorbed on the above-mentioned cold pipe wall. In this way, Hg and the like contained in the atmosphere are rapidly lost.

On the other hand, since the temperature of the growth zone is lowered at a predetermined temperature lowering rate, the temperature is higher than the above-mentioned supersaturated region 17, and a quasi-equilibrium state between the liquid phase and the gas phase is maintained. Therefore, precipitation of Hg etc. does not occur in this part,
It can be said that there is no occurrence of undesirable deposits seen in conventional growth methods.

FIG. 3 is a diagram showing a temperature profile with respect to elapsed time in the growth zone of this example, where the period indicates the period until the growth is completed, and the period indicates the cooling period after the growth is completed. The above period is a temperature rising period, the period is a period when the growth source is completely melted to form the melt 5, and the period is when this melt 5 is CdTe
The period during which the CdTe is transported onto the thin plate 7 and turned into a saturated melt is the period during which the temperature of the melt 5 is raised on the substrate 6 and a portion of the surface of the substrate 6 is melted. It is a period of phase growth.

When the period ends, as described above, the growth zone is slowly cooled at a predetermined cooling rate as shown by the solid line 18 in the figure. On the other hand, the region 17 cooled by means such as blowing high-pressure air is rapidly cooled to form a supersaturated region 17 as shown by a dashed line 19. In addition, in the figure, for convenience of explanation, the temperature of the supersaturated region 17 at the beginning of the period is shown as the same temperature as the growth zone, but since the temperature differs depending on the location where the supersaturated region 17 is provided, the two do not necessarily match.

In order to form the supersaturated region 17, a part of the reaction space is locally rapidly cooled as in the above embodiment, but the method is not limited to air cooling, and any cooling method such as water cooling may be used. It's okay. Furthermore, it is easy to understand that the supersaturated region 17 can be formed anywhere in the reaction space as long as it is outside the growth zone.

Furthermore, the present invention can be used not only to grow a Hg _{1-X Cd} It goes without saying that the present invention is not limited to the one embodiment described above, and that any other means may be used.

As explained above, according to the present invention, the reaction space is made into a quasi-equilibrium system until the liquid phase growth is completed, and during the cooling period after the liquid phase growth is completed, a supersaturated region is created in the reaction space other than the growth zone. By forming a multi-component semiconductor layer that contains easily evaporable components such as Hg, a liquid phase epitaxial growth method that accurately controls the component composition and does not produce deposits on the surface of the grown layer can be achieved. offered.

[Brief explanation of the drawing]

1 to 3 are diagrams showing an embodiment of the liquid phase epitaxial growth method of the present invention, and FIG. 1 is a cross-sectional view of essential parts showing the liquid phase epitaxial growth apparatus used in the above embodiment; FIG. 2 is a diagram showing the temperature distribution in the core tube of FIG. 1, and FIG. 3 is a diagram showing temperature changes over time in the growth zone and supercooled region. In the figure, 1 is the reactor core tube (reaction tube), 5 is the liquid phase,
6 is a substrate, 13 is mercury, 16 is a gas supply pipe, 17
is the supercooled region, 18 is the temperature of the growth zone, 19 is the temperature of the supercooled region, is the period until the liquid phase epitaxial growth is completed, is the cooling period, A is the growth apparatus, B is the mercury evaporation source, C indicates the first high temperature block, and D indicates the second high temperature block.

Claims (1)

[Claims] 1. In a liquid phase epitaxial growth method in which a multi-component semiconductor layer containing an easily evaporable component is grown in an open reaction tube having a gas inlet and a gas outlet, a liquid phase epitaxial growth device and a device for liquid phase epitaxial growth are provided in the reaction tube. , a high-temperature system having a through hole between the source of the easily evaporable component vapor, a predetermined area in which the source of the easily evaporable component vapor and the liquid phase epitaxial growth device are arranged, and the gas outlet; During epitaxial growth, a predetermined area including the growth zone in which the liquid phase epitaxial growth equipment is provided is kept in a quasi-equilibrium state between the liquid phase and the gas phase, and when the epitaxial growth is completed, the predetermined area is cooling at least a portion of the remaining area excluding the growth zone by injecting gas onto the reaction tube wall from outside the reaction tube;
A liquid phase epitaxial growth method, characterized in that the easily evaporable component in the cooling zone is brought into a supersaturated state.