JPH11268904A - Method for synthesizing compound semiconductor polycrystal and compound semiconductor polycrystal synthesized by the method - Google Patents

Abstract

(57) [Summary] [Constitution] A boat in which a raw material of a group III element is placed at one end of an ampoule and a raw material of a group V element is placed at the other end and vacuum sealed. The boat is locally heated to a higher temperature to cause the group III element to react with the group V element vapor generated from the group V element in the boat, and the III-V is gradually moved while relatively moving the high temperature section.
In a polycrystalline synthesis method for synthesizing a group III compound semiconductor polycrystal, the relative movement of the ampule is performed at a lower speed in the initial stage of the synthesis than in the middle stage of the synthesis. [Effect] When the ampoule and the heater are relatively moved, the peak position of the temperature can be prevented from being shifted, whereby the supply of the group V element can be matched with the synthesis speed, and the start end to the end end can be adjusted. Polycrystals whose composition is stoichiometric over a wide range can be synthesized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for synthesizing a compound semiconductor polycrystal, and more particularly to a technique effective for synthesizing an InP polycrystal.

[0002]

2. Description of the Related Art Conventionally, InP used as a material for a compound semiconductor device is composed of raw materials In (indium) and P (indium).
Since it is difficult to grow a single crystal by directly reacting (phosphorus), first, a polycrystal is synthesized, and a single crystal is grown by the LEC method or the like using the synthesized polycrystal. As one of the methods for synthesizing the above-mentioned InP polycrystal, there is a method using a synthesizing apparatus as shown in FIG.

In this synthesis method, a quartz ampule 1 in which a boat 2 containing indium as a raw material is placed at one end and a phosphorus lump 3 is placed at the other end and vacuum-sealed is placed in a synthesis furnace (heater) 4.
As shown in FIG. 2, the temperature of the boat is 800 ° C. and the temperature of the phosphorus mass is 540 ° C.
A temperature distribution having a temperature peak such as 100 ° C. is formed, and the ampoule 1 and the heater 4 are relatively moved to supply phosphorus vapor to the indium in the boat and react, and gradually from one end of the boat to the other end. Then, an InP single crystal is grown. In FIG. 1, reference numeral 5 denotes a heat shield for preventing the temperature in the ampoule from being equalized by convection and facilitating formation of a temperature distribution as shown in FIG.

[0004]

However, in the above-mentioned conventional polycrystal synthesis method, the composition (In / P
Ratio) deviates from stoichiometry (stoichiometric ratio) and tends to be in an indium-rich state with a high indium ratio. In some cases, the terminal portion of the synthetic polycrystal became indium-rich. When a single crystal is grown from a polycrystal containing such an indium-rich portion,
A defect called a micro-twin (or lamella twin) occurs, and a high-quality single crystal cannot be obtained. Therefore, the start and end portions of a conventional indium-rich synthetic polycrystal have to be cut. Therefore, it has been clarified that there is a problem that the waste of the raw material increases and the productivity decreases.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a group III-V compound having a stoichiometric composition over a wide range from the beginning to the end. An object of the present invention is to provide a polycrystal synthesis method capable of synthesizing a semiconductor polycrystal.

[0006]

Means for Solving the Problems In order to achieve the above object, the present inventors first analyzed and considered the cause of the start of synthetic InP polycrystal becoming indium-rich.

As a result, it has been found that in the above-described conventional method, the ampule and the heater are relatively moved, but at that time, the temperature peak position is moved in a direction opposite to the moving direction of the ampule. FIG. 3 shows the relationship between the displacement of the ampoule and the deviation of the temperature peak position obtained by an experiment conducted by the present inventors. In this experiment, however, the ampule was moved at a constant speed with respect to the heater.

When the peak position of the temperature moves in the direction opposite to the moving direction of the ampoule as described above, the relative moving speed between the ampoule and the heater increases, so that the supply of phosphorus cannot keep up with the synthesis speed. As a result, it was concluded that the beginning of the synthetic polycrystal became indium-rich. In addition, it was considered that the reason why the terminal portion of the synthetic polycrystal became indium-rich was that at the end of the synthesis, the amount of phosphorus sublimation was reduced because the phosphorus raw material mass was smaller than the initial mass.

The reason why the temperature peak position shifts as described above is that the heat capacity in the ampoule is larger on the boat side containing indium than on the phosphorus side, so that the boat having a large heat capacity is It is considered that the peak position shifts to the boat side when approaching the peak position side.

[0010] Therefore, the present inventors, by reducing the relative movement speed between the ampoule and the heater at the beginning of the synthesis and at the end of the synthesis, to prevent the temperature peak position from shifting, and to prevent the starting point of the synthetic polycrystal from shifting. Various experiments were carried out on the assumption that it would be possible to avoid the indium-rich portion and the terminal portion from becoming indium-rich. As a result, it has been found that a polycrystal having a stoichiometric composition can be synthesized over a wide range from the beginning to the end by controlling the moving speed.

The present invention has been made on the basis of the above findings. A boat having a raw material of a group III element placed on one end of an ampoule and a raw material of a group V element placed on the other end of the boat is evacuated. The ampoule is sealed, and the whole ampoule is heated, and the boat is locally heated to a higher temperature so that V generated from the group I element and the group V element in the boat.
In the polycrystalline synthesis method of synthesizing a group III-V compound semiconductor polycrystal by reacting with the group element vapor and gradually moving the high temperature part relatively, the relative movement of the ampoule is compared with the relative movement of the ampoule in the early stage of the synthesis, This is done at low speed.

[0012] The relative movement of the ampoule at the end of synthesis may be performed at a lower speed than in the middle of synthesis.

According to the above-described polycrystalline synthesis method, the crystal composition ratio (group III element / (III)) of the synthesized polycrystalline ingot can be increased over a range from 0 to 85%, and depending on conditions, from 0 to 95%. Group element + group V element)) is 0.50
It is possible to obtain a group III-V compound semiconductor polycrystal within the range of 00 ± 0.0001, and it can be expected that waste of raw materials is eliminated and productivity is improved.

The reason for removing the portion having a solidification rate of 85 to 100% is that the higher the solidification rate, the more the impurities are gradually concentrated in the group III element melt by segregation, and the higher the impurity concentration at the crystal termination part. This is because crystals are synthesized.

[0015]

According to the above-mentioned means, it is possible to prevent the temperature peak position from being shifted when the ampoule and the heater are relatively moved, whereby the supply of the group V element can be matched with the synthesis speed. The composition is stoichiometric over a wide range from the beginning to the end III
-Group V compound semiconductor polycrystal can be synthesized.

Further, if the relative movement of the ampoule at the end of the synthesis is changed to a lower speed than that during the middle of the synthesis, the amount of the group V element supplied to the boat decreases even if the mass of the group V element becomes smaller gradually. And the composition is stoichiometric over a wider range III
-Group V compound semiconductor polycrystal can be synthesized.

[0017]

(Example 1) A cylindrical quartz ampoule 1 having an inner diameter of 75 mm and an outer diameter of 80 mm as shown in FIG. 3 was prepared as a synthesis vessel, and one end of the ampoule 1 having a weight of 1.15 kg was prepared. Put red phosphorus ingot 3 and the other end of ampule 1 with 3.9 kg of indium
A 50 mm pBN boat 2 was placed. In addition, a heat shield 5 in which a plurality of quartz disks are held at equal intervals is inserted between the raw materials in the center of the ampoule 1 so that convection inside the ampoule 1 can be prevented. With a quartz cap, and use a vacuum pump to
After the pressure was adjusted to 0 ^-6 Torr, the space between the cap and the ampule 1 was vacuum-sealed using a burner.

Next, the ampoule 1 is placed in a synthesis furnace (heater).
After the temperature was raised from room temperature to 540 ° C. over 2.5 hours, the temperature distribution shown in FIG. 2 was formed and maintained for 1 hour. Then, after moving the ampoule 1 to the right in FIG. 1 at a speed of 4 mm / hour for 7.5 hours (30 mm), the moving speed of the ampoule 1 was increased to a speed of 10 mm / hour, and the InP polycrystal was moved. Was synthesized.

In this embodiment, the polycrystal began to grow 15 mm after the ampoule began to move.

(Example 2) InP polycrystal was synthesized under the same apparatus and conditions as in Example 1, and an ampoule was used.
After moving by 50 mm, the moving speed of the ampoule 1 becomes 6
mm / hr.

(Comparative Example) The moving speed of the ampoule 1 was set to 10 mm during the synthesis under the same conditions as in the first embodiment.
The polycrystalline InP was synthesized at a constant speed of / h.

When the composition ratio In / InP of the synthetic InP polycrystals obtained in Example 1, Example 2, and Comparative Example was measured, the result shown in FIG. 4 was obtained.

In FIG. 4, the symbol □ indicates that the composition ratio In / InP of the synthetic InP polycrystal obtained in Example 1 was plotted, for example, along the growth direction of the crystal ingot, and the symbol ○ indicates the result obtained in the comparative example. Composition ratio In / In of synthetic InP polycrystal
P is plotted along the growth direction of the polycrystalline ingot.

From the above, the composition ratio In / InP of the synthetic InP polycrystalline ingot obtained in the comparative example is largely shifted from the stoichiometry to the indium-rich side at the beginning and the end of the crystal, respectively. The synthetic InP polycrystalline ingot obtained in Example 1 was 34
0 mm (solidification rate 0-85%), the composition ratio In /
It was found that InP was within 0.5000 ± 0.0001.

In the synthetic InP polycrystalline ingot obtained in Example 2, the composition ratio In / InP may be within 0.5000 ± 0.0001 as shown by a mark in FIG. Do you get it.

In the above embodiment, the case where the present invention is applied to the synthesis of InP polycrystal has been described as an example. However, the present invention is not limited to this, and the present invention is not limited thereto. It can be applied when synthesizing a semiconductor polycrystal.

[0027]

As described above, according to the present invention, a boat having a raw material of a group III element loaded on one end of an ampoule and a raw material of a group V element placed on the other end are vacuum-sealed, and the whole ampoule is sealed. While heating, the boat is locally heated to a higher temperature to cause the group III element and the group V element vapor generated from the group V element to react in the boat, while gradually moving the high temperature part relative to each other. In the polycrystalline synthesis method for synthesizing a III-V compound semiconductor polycrystal, the relative movement of the ampoule is performed at a lower speed in the initial stage of the synthesis than in the middle stage of the synthesis. The peak position of the temperature can be prevented from being shifted, so that the supply of the group V element can be matched with the synthesis rate, and the composition can be stored over a wide range from the beginning to the end. Can be synthesized III-V compound semiconductor polycrystalline is Ometori. As a result, waste of raw materials is reduced, and productivity is improved.

When the relative movement of the ampoule at the end of synthesis is also changed at a lower speed than in the middle of synthesis,
Even if the lump of the group V element is gradually reduced, it is possible to prevent the amount of the group V element supplied to the boat from decreasing,
There is an effect that a III-V compound semiconductor polycrystal having a stoichiometric composition can be synthesized over a wider range.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of an InP polycrystalline synthesis furnace.

FIG. 2 is a diagram showing an example of a temperature distribution in an InP polycrystalline synthesis furnace.

FIG. 3 is a graph showing the relationship between the amount of ampoule movement and the deviation of the temperature peak position when the relative movement speed of the ampoule is kept constant during synthesis.

FIG. 4 shows synthetic In obtained in Examples 1 and 2 and Comparative Example.
4 is a graph showing a measurement result of a composition ratio In / InP of P polycrystal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ampoule 2 Boat 3 Phosphorus lump (red phosphorus ingot) 4 Heater (synthesis furnace) 5 Heat shield plate

Claims (4)

[Claims] 1. A boat in which a raw material of a group III element is placed at one end of an ampoule is vacuum-sealed by putting a raw material of a group V element into the other end of the boat, and the whole ampoule is heated and the boat is sealed. Locally heated to a higher temperature, and the V generated from the above-mentioned group II element and the above-mentioned group V element in the boat.
In the polycrystalline synthesis method of synthesizing a group III-V compound semiconductor polycrystal by reacting with the group element vapor and gradually moving the high temperature part relatively, the relative movement of the ampoule is compared with the relative movement of the ampoule in the early stage of the synthesis, A method for synthesizing a compound semiconductor polycrystal, wherein the method is performed at a low speed. 2. The method for synthesizing a compound semiconductor polycrystal according to claim 1, wherein the relative movement of the ampoule in the last stage of the synthesis is also performed at a lower speed than in the middle stage of the synthesis. 3. A compound semiconductor polycrystal synthesized by the method for synthesizing a compound semiconductor polycrystal according to claim 1 or 2, wherein the solidification rate of the polycrystal ingot is 0 to 85.
% Of the crystal composition ratio (Group III element / (I
Group II element + Group V element)) is 0.5000 ± 0.000
A compound semiconductor polycrystal, which is within 1. 4. A compound semiconductor polycrystal synthesized by the method for synthesizing a compound semiconductor polycrystal according to claim 1 or 2, wherein the solidification rate of the polycrystal ingot is 0 to 95.
% Of the crystal composition ratio (Group III element / (I
Group II element + Group V element)) is 0.5000 ± 0.000
A compound semiconductor polycrystal, which is within 1.