JPH0362680B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and apparatus for liquid phase growth of semiconductor crystals, and more particularly to a method and apparatus for growing crystals of - group compound semiconductors by a temperature difference method. .

[Conventional technology and problems]

Conventionally, when growing a semiconductor crystal such as a - group compound semiconductor, for example, as shown in FIG. A heat sink 3 made of a material with high thermal conductivity is attached and fixed to the quartz tube 1, and by forming a cavity below the heat sink 3, even if the heat sink 3 expands in a high-temperature furnace during crystal growth, the quartz tube 1 will not be damaged. In addition to making sure that no distortion occurs, there is also a layer on the heat sink 3 so as to be in close contact with the heat sink 3.
A ZnSe substrate crystal 4 is placed, and the substrate crystal 4 is fixed with a cylindrical quartz substrate stopper 5, and then a Se and Te solvent 6 mixed to have a predetermined composition and ZnSe polycrystalline particles as a growth material are placed. source crystal 7
A growth ampoule 8 is produced by filling the quartz tube 1 with a high vacuum of about 2×10 ^-7 Torr and sealing off the upper end of the quartz tube 1.

The growth ampoule 8 manufactured in this way is set in a heating furnace (not shown) that is preset to a predetermined temperature, and the inside of this heating furnace is heated to a temperature T ₁ at a position A of the substrate crystal 4 and a solvent 6 The temperature T ₂ (T ₂
＞T ₁ ) (see Figure 6), approximately 10℃/
By heating to have a temperature gradient of cm,
A crystal 9 is grown on a substrate crystal 4 placed on a heat sink 3 by a temperature difference method.

In this case, first, invert the upper end of the growth ampoule 8 so that it faces downward, and set the upper end to the growth temperature T ₁
By heating to a higher temperature, ZnSe is uniformly dissolved in Se and Te for about 2 hours, so-called melt alloying is performed to form a melt 6', and then the upper end of the growth ampoule 8 is turned upward. By bringing the melt 6' into contact with the substrate crystal 4 by rotating the melt 6' in the normal direction, the melt 6' is placed on the substrate crystal 4, for example, from 1.0 to
The ZnSe epitaxial growth layer 9 is obtained at a rate of 10.0 μm/hr.

However, when performing melt alloying by inverting the growth ampoule 8, depending on the melt alloying temperature and time, the ZnSe polycrystalline particles 7 may not necessarily be completely dissolved in the solvent 6 to form a uniform melt 6'.
This is not necessarily the case. For example, if the temperature of the melt alloy is low or the time is short, the ZnSe polycrystalline particles 7 will not be completely dissolved in Se and Te of the solvent 6 and will remain. When the growth ampoule 8 is rotated in the normal direction in this state to start crystal growth, the remaining ZnSe polycrystalline particles 7 will fall onto the substrate crystal 4 as described above, and the crystal will grow on the substrate crystal 4. Since the ZnSe polycrystalline particles 7 are mixed in the epitaxially grown layer 9 as they are, it becomes impossible to obtain a good quality epitaxially grown layer 9.

For this reason, conventionally, the proportion of Te in the solvent 6 was increased,
For example, a method has been adopted in which crystal growth is performed at a Se:Te molar ratio of 45:55 or more, but in this method, Te is grown in the epitaxial growth layer 9 grown on the substrate crystal 4. By mixing Te, the epitaxial growth layer 9 becomes ZnSeTe instead of ZnSe, and due to the radius of Te ions, distortion occurs in the crystal constituting the epitaxial growth layer 9. The optical properties of the crystal deteriorate, and in photoluminescence at low temperatures, an energy level with a wide and deep half-value width is generated in the forbidden band width and becomes dominant due to the presence of Te.

[Purpose of the invention]

In view of the above points, the present invention provides a liquid phase growth method that prevents residual ZnSe crystal particles from falling into an epitaxial growth layer grown on a substrate crystal without increasing the proportion of Te in the solvent. and a growth device.

[Means and actions for solving problems]

The above object, according to the present invention, includes two quartz tubes of different diameters connected to each other, the lower end of the lower first quartz tube of small diameter is sealed flat, and the first quartz tube is For growth, a heat sink is attached so as to be in contact with the inner wall of the tube, a solvent and a source crystal are placed in a large-diameter second quartz tube on top of the heat sink, and the upper end of the second quartz tube is sealed under high vacuum. In a temperature difference liquid phase epitaxial growth method or a growth apparatus for - group compound semiconductors, in which a semiconductor crystal is grown using an ampoule, a cast crystal with dimensions larger than the inner diameter of the first quartz tube is used as a source crystal. This is achieved by using lumps.

According to this invention, since an ingot is used as the source crystal, even if the source crystal remains without being completely dissolved in the solvent after the growth ampoule is inverted and melt alloying is performed, the remaining The source crystal is selected to have a size larger than the inner diameter of the small-diameter first quartz tube that forms the growth ampoule, so that it can be used as an ingot in the form of a first quartz tube. The source crystal is supported by the step formed in the connection area with the second quartz tube, so particles of the source crystal will not be mixed into the epitaxial growth layer during crystal growth, and the melt will be uniform. This means that it can be maintained as follows.

Furthermore, since it is possible to set the mixing molar ratio of Se and Te in the solvent to any value, the crystals forming the epitaxial growth layer grown on the substrate crystals can optically emit light due to Te. There are very few
Or it will be of no good quality at all.

Furthermore, if the step part is located in the melt, the source crystal will be in contact with the melt during crystal growth, so by appropriately selecting the amount of the source crystal ingot, it will be possible to Spanning crystal growth is easily achieved, resulting in relatively thick epitaxially grown layers. In addition, if the step is located above the melt surface, the source crystal will not be in contact with the melt during crystal growth, so crystal growth will be limited by the amount of melt, and the melt alloying time will be limited. The thickness of the epitaxially grown layer depends on the melt alloying time and temperature since the amount of source crystal melted is determined based on By controlling the melt alloying time and temperature, an epitaxially grown layer of desired thickness can be obtained.

〔Example〕

The present invention will be described in detail below based on an embodiment shown in the drawings.

FIG. 1 shows a growth ampoule used in an embodiment of a liquid phase growth apparatus for carrying out the present invention, and this growth ampoule 10 has an inner diameter of, for example, 8.
A first quartz tube 11 having a small diameter of 12 mm to 12 mm and a second quartz tube 12 having a large diameter having an inner diameter of 15 to 20 mm are connected in an upright position with the first quartz tube 11 positioned downward. The lower end of the first quartz tube 11 is sealed flat, and a heat sink 13 with a height of, for example, 80 to 200 mm is placed in contact with the inner wall of the first quartz tube 11.
is attached and fixed with a slight cavity left at the lower end of the first quartz tube 11 so as to absorb the expansion of the heat sink 13 in the high-temperature furnace, and furthermore, it is placed on the heat sink 13 so as to be in close contact with the heat sink 13. to
A ZnSe substrate crystal 14 is placed, the substrate crystal 14 is fixed with a cylindrical quartz substrate stopper 15, and then a Se, Te solvent 16 with an arbitrary predetermined mixing ratio is introduced into the second quartz tube 12 of the growth ampoule 10. After placing a source crystal 17 of ZnSe, which is a growth material, on top of it, the upper end of the second quartz tube 12 is sealed in a high vacuum of, for example, about 2 × 10 ^-7 Torr. Its total height is, for example, 180 to 300 mm.

In this case, the source crystal 17 is an ingot such as a sintered body, and its size is selected to be larger than the inner diameter of the first quartz tube 11 and smaller than the second quartz tube 12. When housed in the quartz tube 12, it is supported by gravity on a step 11a formed in the connection area between the first quartz tube 11 and the second quartz tube 12.

This apparatus is constructed as described above, and when performing crystal growth, the growth ampoule 10 is first inverted into a heating furnace, as in the case of the conventional growth ampoule 8 shown in FIG. After setting and performing melt alloying, the growth ampoule 10
When the source crystal 17 is rotated in the normal direction to start crystal growth, even if the source crystal 17 remains during melt alloying, the source crystal 17 is not a polycrystalline particle but an ingot, so the source 17 will be removed during crystal growth. Substrate crystal 14
A uniform and high quality epitaxial growth layer 18 can be grown.

At this time, since the second quartz tube 12 is filled with the melt 16' up to above the step portion 11a, the source crystal 17 is in contact with the melt 16' as shown in the figure, and the source crystal 17 is in contact with the melt 16' as shown in the figure. By appropriately selecting the amount of 17, a relatively thick epitaxial growth layer 18 can be easily obtained over a long period of time.

Next, an experimental example is shown in Figure 2. In the liquid phase growth of ZnSe, the mixing ratio of Se and Te as solvents was changed.
50:50, using substrate crystals with the same plane orientation, and keeping the growth conditions the same.
Minutes of melt alloying was followed by 3 hours of crystal growth.

As a result, with conventional equipment, the height of the center of the crystal
lc is 20 to 25 μm, peripheral height lc is 9 to 12 μm
In contrast, ZnSe polycrystalline particles fall onto the substrate crystal in the early stage of growth, and the surface of the epitaxial growth layer 9 has many irregularities and pores may be formed (see FIG. 2A). In the device of the present invention, the height lc of the central portion of the crystal is 9 to 11 μm, and the height lc of the peripheral portion is 5 to 7 μm, and the surface is smooth and almost mirror-like (see FIG. 2B).

In addition, when measuring the photoluminescence of the epitaxially grown layer, the mixing ratio of Se and Te in the solvent can be determined as follows:
In the conventional example with 45:55, as shown in Figure 3A, the half-width is wide with a peak of about 2.65 eV.
While photoluminescence occurs due to Te, when using the apparatus of the present invention with the above mixing ratio of 85:15, the above-mentioned peak does not occur as shown in Figure 3B, and DA Paired luminescence can be confirmed.

FIG. 4 shows a modification of the device shown in FIG.
This growth ampoule 10' has the same structure as the growth ampoule 10 shown in FIG. 1, except that the melt 16' is not filled below the step 11a, that is, into the first quartz tube 11. It is.

In this case, the effect is almost the same as that of the growth ampoule 10 shown in FIG. 1, and since the source crystal 17 is not in contact with the melt during crystal growth, the crystal growth is limited by the amount of melt. Therefore, the thickness of the epitaxially grown layer 18 can be adjusted as desired by appropriately controlling the melt alloying time and temperature.

〔Effect of the invention〕

As described above, the present invention includes two quartz tubes of different diameters connected to each other, the lower end of the lower first quartz tube of small diameter is sealed flat, and the lower end of the first quartz tube of small diameter is sealed flat. A heat sink is attached so as to be in contact with the inner wall of the quartz tube, and the solvent and source crystal are placed in a large-diameter second quartz tube above the heat sink, and the upper end of the second quartz tube is sealed under high vacuum. In a temperature difference liquid phase epitaxial growth method or growth apparatus for a - group compound semiconductor in which a semiconductor crystal is grown using a quartz ampoule, a cast quartz tube with dimensions larger than the inner diameter of the first quartz tube is used as a source crystal. Since this liquid phase epitaxial growth method or growth apparatus is configured to use an ingot, an ingot is used as a source crystal, so after inverting the growth ampoule and performing melt alloying,
Even if the source crystal does not completely dissolve in the solvent and remains, the size of the remaining source crystal is selected to be larger than the inner diameter of the small-diameter first quartz tube forming the growth ampoule. As a result, the source crystal particles are supported in the form of an ingot by the step formed in the connection area between the first quartz tube and the second quartz tube, and the particles of the source crystal are supported during crystal growth. The melt will not be mixed into the epitaxially grown layer, and the melt can be maintained uniformly.

In addition, since it is possible to set the mixing molar ratio of Se and Te in the solvent to an arbitrary value, the crystals forming the epitaxial growth layer grown on the substrate crystals can optically emit light due to Te. There are very few
Or it will be of no good quality at all.

Furthermore, if the step part is located in the melt, the source crystal will be in contact with the melt during crystal growth, so by appropriately selecting the amount of the source crystal ingot, it will be possible to Spanning crystal growth is easily achieved, resulting in relatively thick epitaxially grown layers. In addition, if the step is located above the melt surface, the source crystal will not be in contact with the melt during crystal growth, so crystal growth will be limited by the amount of melt, and the melt alloying time will be limited. The thickness of the epitaxially grown layer depends on the melt alloying time and temperature since the amount of source crystal melted is determined based on By controlling the melt alloying time and temperature, an epitaxially grown layer of desired thickness can be obtained.

Thus, according to the present invention, a temperature difference liquid phase epitaxial method is achieved in which residual ZnSe crystal particles do not fall onto the substrate crystal and a high-quality epitaxial growth layer is obtained without increasing the proportion of Te in the solvent. A growth method and a growth apparatus may be provided.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of an embodiment of a liquid phase growth apparatus for carrying out the present invention, FIG. 2A is an enlarged sectional view of an epitaxially grown layer by a conventional apparatus, and FIG. FIG. 3 is an enlarged cross-sectional view of an epitaxially grown layer by the apparatus. FIG. 3A is a graph showing the photoluminescence characteristics of the epitaxially grown layer produced by the conventional apparatus, and FIG. 3B is a graph showing the photoluminescence characteristics of the epitaxially grown layer produced by the apparatus of FIG. FIG. 4 is a schematic sectional view similar to FIG. 1 showing another embodiment of the present invention. Fifth
The figure is a schematic sectional view showing an example of a conventional liquid phase growth apparatus, and FIG. 6 is a graph showing the temperature gradient in the apparatus of FIG. 10... Ampoule for growth; 11... First quartz tube; 12... Second quartz tube; 13... Heat sink; 14... Substrate crystal; 15... Substrate stopper; 16
...solvent; 17...source crystal; 18...crystal-grown epitaxial growth layer.

Claims (1)

[Scope of Claims] 1. Includes two interconnected quartz tubes of different diameters, the lower end of a lower first quartz tube of small diameter is sealed flat, and the inner wall of the first quartz tube is sealed so as to be flat. A growth ampoule is used in which the solvent and source crystal are placed in a large-diameter second quartz tube on top of the heat sink, and the upper end of the second quartz tube is sealed in a high vacuum. In a temperature difference liquid phase epitaxial growth method for - group compound semiconductors in which a semiconductor crystal is grown by using a method for crystal growth, an ingot having a size larger than the inner diameter of a first quartz tube is used as a source crystal. A liquid phase epitaxial growth method characterized by: 2. It includes two interconnected quartz tubes with different diameters, the lower end of the lower first quartz tube of small diameter is sealed flat, and a heat sink is attached so as to be in contact with the inner wall of the first quartz tube. Place the solvent and source crystal in a large-diameter second quartz tube on top of the heat sink, and crystallize the semiconductor crystal using a growth ampoule with the top end of the second quartz tube sealed under high vacuum. In a temperature difference liquid phase epitaxial growth apparatus for - group compound semiconductors,
A liquid phase epitaxial growth apparatus characterized in that a source crystal is an ingot having a size larger than the inner diameter of the first quartz tube.