JPS6041040B2 - How to grow gallium phosphide semiconductor crystals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for growing a Gap (gallium phosphide) semiconductor crystal using the SSD method, and more particularly, to a crystal growth method capable of obtaining a large Gap single crystal.

The SSD method for making GaP semiconductor crystals was developed in Samurai Kosho 48-20.
It is publicly known from Publication No. 106 and the like.

Next, a typical conventional gap crystal growth method using this SSD method will be explained with reference to FIGS. 1 and 2. A seed crystal 2 is placed at the bottom of a cylindrical crucible 1 made of quartz as shown in FIG.
Put a Ga solution 3 on top of this, and hold this crucible 1 with a supporting member (
(not shown) and placed on the upper part of the sealed quartz container 4. Further, red phosphorus 5 in an amount of 4 to 5 skins in height is placed at the bottom of a sealed container 4 made of quartz, and the container is vacuum-sealed to about 10-6 Troops. Next, this red neighbor 5 is heated to about 43,000 by using the first heater 6.
to generate a P vapor pressure of about 1 atmosphere in the container 4. Further, as shown in FIG. 2, a temperature gradient is applied to the Ga solution 3 using the second heater 7 so that the P2 position on the surface of the Ga solution 3 is, for example, 115,000, and the P position of the seed crystal 2 is, for example, 1,000oo. give. In this way, Ga solution 3
Gap is synthesized on the surface of the GaP film 8, and this G
ap diffuses as a solute in the Ga solution 3 toward the seed crystal 2, and a Gap crystal 9 begins to grow on the seed crystal 2. After the growth of crystal 9 has started, the temperature gradient between the crystal plane position P' and the ○a solution surface position P2 causes GaP
continues to diffuse, and the growth of the Gap crystal continues. That is, the synthesis (Synthe
The compound GaP (SiS) is passed through the Ga solution 3 as a solute and the seed crystal 2 or the already grown Ga
Diffusion toward the low-temperature part of the surface of the p-crystal 9
on) and GaP crystal 9 grows. SSD as mentioned above
Although this method has the disadvantage of slow crystal growth,
It has many advantages as follows: {a} Unlike the widely used LEC method, there is no need to grow crystals at high temperatures and pressures, making the manufacturing equipment simple and inexpensive. Manufacturing is easy because crystals are directly formed using elements constituting other compound semiconductors as starting materials. [c) Since the shape of the crystal is determined by the shape of the container (crucible), crystals with uniform diameter can be obtained. 'd- Since a crystal with few crystal defects can be obtained, a light emitting device with high luminous efficiency can be obtained. However, if a crystal is grown by the secondary SSD method using the apparatus shown in FIG. The crystals were lined up9, that is, polycrystalline, and it was difficult to obtain a large single crystal.

Therefore, when making a light emitting device using this crystal 9, there are always disadvantages due to the fact that it is polycrystalline. For the purpose of producing a large single crystal, Japanese Patent Publication No. 48152/1983 proposes a method of keeping the temperature of the surface of the Ga solution and the temperature of the Gap crystal growth surface constant.

This method is different from the conventional SSD method as shown in Figure 1.
As the GaP crystal 9 grows, the Gap crystal growth surface and the G
Based on the idea that it is difficult to produce a single crystal because the surface position of the a solution 3 changes and the temperature and temperature distribution of these parts change, as illustrated in FIG. 5, For example, G
a The cross-sectional area of the upper part of crucible 1 containing solution 3 is 1/1/of the lower part.
2, the crucible 1 is moved downward in accordance with the growth of the GaP crystal 9 on the seed crystal 2, and the temperature TH of the surface of the Ga solution and the Gap crystal 9, where Ga and P react to form the Gap film 8, are
This is a method of keeping the temperature TL of the growth surface and the distance L between these two surfaces constant during crystal growth. However, even if the temperature conditions are kept constant in this way, it is extremely difficult to reliably obtain a large single crystal. Therefore, an object of the present invention is to provide a method for growing a Cap crystal using the SSD method, which allows obtaining a single crystal or a crystal close to a single crystal.

To achieve the above object, the present invention provides a method for disposing a container containing a Ga solution exhibiting a relatively low vapor pressure in an atmosphere containing S vapor exhibiting a relatively high vapor pressure; The part of the Ga solution that comes into contact with the vapor is a high temperature part that is lower than the melting point of GaP made of Ga and P but has a relatively high temperature, and the part of the Ga solution that is away from the high temperature part is lower in temperature than the high temperature part. The vapor pressure of the P is set as the low temperature part, and the vapor pressure of the P is set as the low temperature part.
The Ga synthesized in the high temperature section is made higher than the decomposition pressure of p.
In the method of growing a Gap semiconductor crystal in the low temperature region by diffusing p into the Ga solution, a Gap seed crystal is placed at the bottom of the container containing the Ga solution, and the GaP
A heat radiator (heat sink) is thermally coupled to the seed crystal, and the Ga solution and the P vapor react to synthesize Gap.The area (S,) of the surface of the Ga solution and the low temperature The ratio (S,
/S2) to 1/I. 7 to 1'5, and a GaP semiconductor crystal is grown with an average temperature gradient of 15 to 40 q/m between the surface of the Ga solution and the crystal growth surface of the GaP crystal. It is related to the method of growth.

According to the present invention, the effect of the heat sink, the area ratio S,
The effect of 'S2 and the effect of the average temperature gradient act synergistically to produce a large single crystal or a crystal close to a single crystal.

Embodiments of the present invention will be described below with reference to FIGS. 6 to 13.

However, the items indicated by numerals 1 to 9 in Figs. 6 to 13 are substantially the same as those indicated by the same numerals in Fig. 1, and the basic manufacturing method is also the same. Explanation of these items will be omitted. In FIG. 6 showing the GaP crystal growth apparatus according to the embodiment of the present invention, the lower la of the quartz crucible 1 is
A GaP seed crystal 2 having a 1 1 1 crystal growth plane is arranged, and a thin graphite plate 1 is placed under this Gap seed crystal 2.
A heat sink 10 made of silicon for temperature gradient adjustment is arranged through the heat sink 10' and the container 10.
It is supported by a plurality of protrusions 11 fixed to.

Therefore, the crucible 1 does not have a bottom, and the seed crystal 2, the graphite plate 10a, and the heat sink 10 serve as the bottom.
Even if the crucible 1 does not have a bottom, the Ga solution 3 will not flow out due to the surface tension of the Ga solution 3. The crucible 1 has a large diameter part lb and a small diameter part lc, and the N-type impurity is added so that the surface of the Ga solution 3, that is, the portion of the Ga film 8 is located in the small diameter part lc during the entire period of crystal growth. A Ga solution 3 doped with Te is injected. 4. The small light part lc is adjusted so that the ratio S,/S2 of the surface area S of the Ga solution 3 in the light part lc to the area S2 of the growth surface of the Gap crystal 9 in the large diameter part lb is approximately 1/3. The inner diameter of the large flange lb is determined to be approximately 24 ribs, and the inner diameter of the large flange lb is determined to be approximately 42 ribs. When growing the Gap crystal 9 using the apparatus shown in Fig. 6, the temperature TH of the high temperature section corresponding to the P2 position in Fig. 6 is set to 1200q○ or less to avoid contamination by Si in the quartz. And also P
, the temperature T of the Gap crystal growth surface in the low temperature part corresponding to the position is set to 950 to 1100 o'clock, and the average temperature gradient (hereinafter simply referred to as temperature gradient) in the Ga solution 3 is set to 15 qo/skin or more.

That is, as shown in FIG. 7, there is a temperature difference TH between P and P2 positions.
-TL is caused, and the temperature gradient due to this temperature difference is set to an appropriate value selected from 15 to 40 degrees/arc.
In Figure 7, TP is the heating temperature of red phosphorus 5, which is about 420~
It is set to 450oo. Here, the temperature gradient in the Ga solution 3 is set to 15° C./2 or more, but when obtaining a crystal ingot with a diameter of about 3 m or more, the temperature gradient in the Ga solution 3, which is a metal and has high thermal conductivity, is It was difficult to obtain a temperature gradient of 1000/skin or more.

The reason why it was not possible to reliably obtain a single crystal using the method disclosed in Japanese Patent Publication No. 51-48152 is that a sufficient temperature gradient was not created in the Ga solution 3 even though the temperature of the heating furnace was set accurately. It is presumed that one reason for this is that they were not. Therefore, in this example, the temperature of the crystal growth surface is forcibly lowered by using a heat sink made of silicon, which has high thermal conductivity and heat resistance.
A temperature gradient greater than C/inhibition was obtained. In this example, the temperature gradient within the Ga solution 3 during crystal growth increases with time, as shown in FIG. 11. However, 15~
40:00/kept within range of the enemy. When the temperature gradient is set as described above and the crucible 1 having the small diameter part lc and the large diameter part lb is set to S,/S2=1/3, the Gap film 8
The concentration of Gap that diffuses toward the seed crystal 2 or the growing crystal 9 suddenly decreases at the point where it moves from the small diameter portion lc to the large diameter portion lb.

FIG. 10A shows the concentration of GaP in the Ga solution 3 from the surface position P2 of the Ga solution 3 to the growth surface position P of the crystal 9, and the boundary position Pc between the small depression lc and the large depression lb.
This shows that the GaP concentration decreases rapidly at , and then gradually decreases toward the crystal growth surface. By the way, the saturation concentration of GaP is determined by the temperature, and when the temperature gradient in the Ca solution is almost constant, experimental data shows that the saturation concentration of GaP is a curve that protrudes slightly downward in an arch shape, as shown in curve B in Figure 10. expressed.

As is clear from the comparison between this GaP saturation concentration curve B and the GaP concentration curve A of this example, the GaP concentration of this example is limited to below the saturation concentration in the large portion lb of P, ~Pc. There is. In other words, the concentration distribution is such that no supersaturation occurs. Therefore, even if a stimulus such as vibration is applied, a crystal nucleus that causes polycrystals is generated, and a large single crystal portion 9a as shown in FIGS. 8 and 9 can be obtained. Although a small amount of polycrystalline portion 9b is formed in the outer peripheral region that contacts the crucible 1, it is much smaller than the single-crystalline portion 9a. According to the present example, as described above, it is possible to grow the whole as a substantially single crystal, whereas in the secondary method shown in FIG. 1, a polycrystal is grown as shown in FIGS. The reason for this is thought to be that the GaP concentration distribution in the Ga solution 3 is as shown by curve C in FIG. 10.

That is, in the case as shown in FIG.
The concentration distribution of Gap as a solute from the side of the GaP film 8 with a high concentration to the side of the crystal growth surface with a low concentration is slightly arched upward according to Fick's first law. The curve becomes a prominent curve C, and all regions are in a supersaturated state or a state close to this. For this reason, it is thought that stimulation such as vibration tends to generate crystal nuclei that cause polycrystals, resulting in crystals 9 as shown in FIGS. 3 and 4. In order to investigate how the value of S, /S2 and crystal growth are related, in the apparatus shown in Fig. 6,
The inner diameter of the large part lb, that is, the value of S2, is constant, and the small light part lc
When only the internal strain, ie, S, was varied, the change in the number of single crystal grains in the ingot was investigated, and the graph shown in FIG. 12 was obtained. In this graph, curve a is S,/S2
= 1, curve b is S, /S2 = 1/1.5,
Curve c is S, when /S2=1/1.7, curve d is S,
/S2=1/2, the curve e is S. /S2=1/2.
5 S. /S2=1/3 and S, /S2=1/4 and S
．． The relationship between the growth time and the number of single crystal grains (pieces/grain) when /S2=1/5 is shown. The axis of this graph is a parameter representing the crystal state at each point from the start to the end of crystal growth, and is called the growth order. As the crystal grows, the number of single crystal grains increases, but in curves c, d, and e, the number of single crystal grains remains substantially 1 until near the end of growth. On the other hand, curves a and b include many monocrystalline grains. Therefore, when S,/S2≦1/1.7, the number of single crystal grains is extremely small, and a crystal that can be substantially regarded as one large single crystal can be obtained. However, as S,/S2 becomes smaller, the crystal growth rate slows down and becomes impractical, so S,/S2=1/9 degree is the limit. Although the crystal growth rate is also related to the temperature gradient within the Ga solution 3,
For a realizable temperature gradient of 15 to 40 oo/h, the practical limit of S,/S2 is about 1/5. Furthermore, although the number of single crystal grains in FIG. 12 was determined visually, if the microcrystalline state was examined using a photoelastic method instead, it was found that S. The crystals grown at /S2il/1.7 and 1/2 have areas where small regions with minute angles called micrograins are concentrated, and S
, /S2≦1/2.5, almost no micrograins were observed in the crystals grown. Light emitting diodes using crystal parts containing micrograins have poor light emitting characteristics, so S. The value of /S2 is more preferably 1/2.5 or less. In the crystal growth method using the decoction shown in Figure 6,
The single crystal state of the Gap crystal was investigated when the temperature gradient in the Ga solution 3 was varied. As a result, the temperature gradient is 1ooo
/ At skin level, the Ga solution 3 is in an unstable state where crystal nuclei are easily formed, and crystal nuclei that become the source of polycrystals are formed during GaP diffusion, resulting in large single crystals with good reproducibility. I couldn't get it. When lyC/ or more, the Ga solution was in a relatively stable state, and GaP crystals with few large single crystal grains could be obtained with good reproducibility. However, if the temperature gradient is made too large, the crystal growth rate will increase, but at the same time, crystal defects will increase, so it is not preferable to exceed about 40° C./skin. Note that by increasing the temperature gradient as the crystal grows, a crystal closer to a single crystal can be obtained. In the apparatus shown in FIG. 6 and the crystal growth method using the same, since the silicon heat sink 10 is used, it was possible to obtain a temperature gradient of 15 to 40 oo/g in the Ga solution 3.

In order to create a large temperature gradient of 1500/skin or more without using this heat sink 10, the position of crucible 1 is I tried shifting it from heater 7 by an appropriate distance. However, although the expected temperature gradient was obtained with this method when crucible 1 was empty, when Ga solution 3 was placed in crucible 1, only a small temperature gradient was obtained due to the high thermal conductivity of Ga. Ta. For example, when the crucible 1 was empty, a temperature gradient of 30 qo/kg was obtained, but when the Ga solution 3 was put into the crucible 1 and the temperature gradient was actually measured, it was less than 10 qo/kg. Therefore, the method of thermally coupling the heat sink 10 to the seed crystal 2 is a simple and practical method for making the temperature gradient in the Ga solution 3 greater than 15 qo/skin. In addition, there are two cases in which a crystal is grown using an induction heating furnace capable of local heating as the heater 7 and a temperature gradient larger than that in a general resistance heating furnace, and a case in which a crystal is grown using the heat sink 10 of this embodiment. When compared with the case where the heat sink 10 is grown, it was found that the use of the latter heat sink 10 yields a GaP crystal with fewer crystal grains, that is, a large single crystal, with better reproducibility. The reason for this is not clear, but by using the heat sink 10, the temperature at the center of the circular crystal growth surface becomes slightly lower than the surrounding temperature, and the temperature distribution due to this temperature difference and S, /S2≦1 This seems to be because the effect of setting the value to /1.7 is acting synergistically. Next, FIG. 13, which shows a GaP crystal growth apparatus according to another embodiment of the present invention, will be described. However, parts that are substantially the same as those in FIG. 6 are given the same reference numerals, and their explanations will be omitted. In this example,
Instead of providing the small diameter portion lc of the crucible 1 shown in FIG.
It's floating in the air. Then, this float 12 changes the area of the contact surface between the Oa solution 3 and the neighboring P vapor made of red phosphorus 5, that is, the upper surface of the Ga solution 3, and the contact area between the seed crystal 2 or the growing crystal 9 and the Ga solution 3, that is, the area of the upper surface of the Ga solution 3. It is formed so as to be limited to about 1/3 of the area of the upper surface of the crystal. In addition, in order to reliably maintain the limit on the contact area between Ga and P from the start to the end of crystal growth, a pulling device 13 is installed to pull up the float 12 in accordance with changes in the height of the liquid level of the Ga solution 3. It is provided. Although not shown in the drawings, a sealing device is provided to prevent phosphorus P vapor from escaping even if the pulling refit 13 is provided. In this configuration, GaP that has started to diffuse from the Gap film 8 passes through the float 12 and suddenly enters the portion of the Ga solution 3 that has a large cross-sectional area, so that the concentration of Gap in the Ga solution 3 is equal to that of the flow. - It suddenly decreases below the first
A concentration distribution similar to that in Figure 0 was obtained, with a temperature gradient of 15 to 40°C.
/ Due to the synergistic effect with the skin effect, single crystals can be obtained with good reproducibility as in the case of Fig. 6.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and can be further modified without departing from the gist of the present invention.

For example, the present invention is not limited to manufacturing ingots, but can also be applied to epitaxially growing a thin GaP layer on a substrate. Alternatively, the float 12 may be held or moved by electric or magnetic force. Moreover, the heat sink 10 may be made of materials other than silicon. Alternatively, the growth may continue without providing the lifting device 13 for the float 12 even if it becomes impossible for the float 12 to float on the surface of the Ga solution 3. Furthermore, an anti-adhesion plate other than the graphite plate 10a may be interposed between the heat sink 10 and the seed crystal 2.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing a conventional SSD method equipment, Figure 2 is a temperature distribution diagram showing the temperature distribution of the equipment shown in Figure 1, and Figure 3 is a cross-sectional view of a crystal made by the counterfeiting method shown in Figure 1. , Figure 4 shows W in Figure 3.
It is a sectional view of a portion corresponding to the -W line. FIG. 5 is a temperature distribution diagram illustrating another example of the conventional SSD method. FIG. 6 is a cross-sectional view of a manufacturing apparatus according to an embodiment of the present invention, FIG. 7 is a temperature distribution diagram of the reloading shown in FIG. 6, and FIG. 8 is a cross-sectional view of the crystal made by the reloading of FIG. 6. FIG. 9 is a cross-sectional view corresponding to the line K in FIG. 8, and FIG. 10 is a graph showing the relationship between the orientation and the Gap concentration in the Ga solution in the apparatus of FIG. 6. Fig. 11 is a graph showing the relationship between growth time and temperature gradient in the apparatus shown in Fig. 6, and Fig. 12 is a graph showing the growth order and growth rate when the size of the small diameter section is changed in the apparatus shown in Fig. 6. It is a graph showing the relationship with the number of crystal grains. FIG. 13 is a sectional view of a growth apparatus according to another embodiment of the present invention. In addition, in the symbols used in the drawings, 1 is the crucible,
2 is a seed crystal, 3 is a Ga solution, 4 is a container, 5 is red phosphorus, 6 is a first heater, 7 is a second heater, 8 is a Gap film,
9 is a Gap crystal, and 10 is a heat sink. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 12 Figure 13 Figure 10 Figure 11

Claims (1)

[Claims] 1. A container containing a Ga solution exhibiting a relatively low vapor pressure is placed in an atmosphere containing P vapor exhibiting a relatively high vapor pressure,
The part where the Ga solution contacts the P vapor is separated by Ga and P.
a high temperature part having a relatively high temperature but lower than the melting point of GaP consisting of; a part of the Ga solution remote from the high temperature part as a low temperature part having a temperature lower than the high temperature part;
In the method of growing a GaP semiconductor crystal in the low temperature region by increasing the vapor pressure of the GaP to a higher temperature than the decomposition pressure of the GaP and diffusing the GaP synthesized in the high temperature region into the Ga solution, the GaP semiconductor crystal is grown in the low temperature region. A GaP seed crystal is placed in the lower part of the container, a heat radiator is thermally coupled to the GaP seed crystal, and the Ga solution and the P vapor react to synthesize GaP. The ratio (S_1/S_2) of the surface area (S_1) to the crystal growth surface area (S_2) of the GaP crystal at the low temperature is set to 1/1.7 to 1/5, and the
A method for growing a GaP semiconductor crystal, the method comprising growing a GaP semiconductor crystal at an average temperature gradient of 15 to 40° C./cm between the surface of the solution and the crystal growth surface of the GaP crystal.