JPH01133998A - Liquid phase epitaxy for sic single crystal - Google Patents

Abstract

PURPOSE:To obtain the title single crystal capable of increasing the yield of a blue light emitting diode and having excellent crystallinity with good reproducibility by dipping an SiC single crystal substrate in the Si melt in a graphite crucible so that the distance between the substrate and the crucible bottom is kept within specified limits. CONSTITUTION:The Si melt 5 is filled in the graphite crucible 4 set on a susceptor 3 in a quartz reaction tube 1 around which a highfrequency coil 2 is wound in the device for liq. epitaxy for an SiC single crystal. The 6H-SiC single crystal substrate 8 set in the V-shaped notch 7 formed on the lower end of a substrate supporting rod 6 is dipped in the melt 5 so that the distance between the bottom of the crucible 4 and the substrate 8 is controlled to <=3mm, and an SiC single crystal is grown under specified conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a method for liquid phase epitaxial growth of SiC single crystals.

(b)) Conventional technology 81 (3 single crystal has a forbidden band width of 2.398 V to 5.3
It has the advantage that it has a wide range of 3ay, and that it is easy to form a slanted pn junction where P-type and n-type crystals can be obtained.

Among them, α-type 6H-s1c single crystal has a crystallinity of about 5 at room temperature.
．． It has a forbidden band width of QeV and is used as a material for blue light emitting diodes. This blue light emitting diode is a 6H type n-type 8 on a 6H type or 4H type 810 single crystal substrate.
10 layers and a p-type SiO layer are grown epitaxially. The above layers are grown in a graphite crucible with a temperature gradient that gradually increases the temperature from the bottom to the top. This is done by immersing the substrate in the melt for a certain period of time (Electronic Technology Vol. 26, No. 14, p. 12).
8-129).

(c) Problems to be Solved by the Invention In the above-mentioned method, crystal defects such as carbon vacancies in the growing crystal cannot be reduced, no matter how much the temperature gradient of the melt is adjusted. As a result, blue light emitting diodes produced using the above method tended to have longer emission wavelengths and lower brightness, and the yield did not improve.

Ninth Means for Solving the Problems The present invention has been made in view of the above-mentioned problems. An 81G single crystal substrate is immersed in 81 melt in a graphite crucible, and a SiO single crystal is deposited on the substrate. The purpose is to set the distance between the substrate and the bottom of the crucible to 6 or less during growth.

(e) Effect When the SiO single crystal substrate is grown within six layers from the bottom of the crucible in this way, the nine layers grown have good crystallinity.

Figure 1 shows the apparatus used in the experiment leading to the present invention.
) is a reaction tube made of quartz, (2) is a high-frequency coil wound around the reaction tube, (3) is a susceptor placed inside the reaction tube (1), and (4) is placed on the susceptor. The placed graphite crucible, (5) is housed in the crucible and contains the nine-Si melt, (6)
is a substrate support rod, and the lower end of the support rod is 81 melt (
5) Supported so as to be immersed in it. (7) is a 7-shaped notch formed at the lower end of the support rod (6), and (8) is a 6H-8i○ single crystal substrate, which is attached to the notch (7). 〇Also, the above experiment was carried out using a silicon melt with a gradient (hereinafter simply referred to as temperature gradient) in which the number of layers was maintained at about 1,700 and the temperature increased from the bottom to the top at a rate of 4'C/1. The distance d from the bottom of the crucible (4) to the surface of the substrate (8) opposite to the bottom when a 6H-310 single crystal layer was grown by dipping the substrate (8) in (5) and the distance of the growth layer. The relationship between the rocking curve (diffraction intensity curve) and the half width was investigated. Note that the rocking curve half-width is the half-width of a diffraction line peak measured by X-ray diffraction, and the smaller the half-width, the better the crystallinity.

FIG. 2 shows the results of such an experiment. As is clear from FIG. 2, when the distance d increases by more than 3, the half width increases and the crystallinity decreases.

Although the reason for this is not clear, the heat dissipation effect through the susceptor (3) is large, and as a result, an extremely cold spot is created relatively near the bottom of the crucible (4), and the cold spot and its vicinity are It is thought that this is because the carbon atoms dissolved from the side wall of the crucible (4) are concentrated, thereby suppressing the generation of carbon vacancies in the growing crystal.

Note that even when the temperature gradient of the Si melt (5) is changed, the second
Similar to the results shown in the figure, it was confirmed through actual tests that when the distance -d was greater than 6, the crystallinity sharply decreased.

(f) Example As an example of the present invention, an n-type 6)I-8iO layer doped with nitrogen and aluminum and an aluminum-doped A blue light emitting diode was fabricated by stacking p-type 6H-1310 layers. The growth conditions for each growth layer above are as follows.01) Growth conditions for n-type 6H-8iO layer Melt temperature: 1650-1700 Layer temperature gradient: 4°C/cm Distance d: 3 Molten material: 81+EliN+ A small amount of AI! 11) p-type 6
Growth conditions for H-8iO layer Melt temperature: 1650-1700 Layer temperature gradient: 4°C/Country distance a: 3mm Melt material: 31+AI! When a blue light emitting diode is created under these conditions, the emission wavelength is 480 nm or less at a lateral current of 20 fflA,
The yield rate of light emitting diodes with a luminous intensity of 2 mCa or more is 70
%Met.

In addition, under the above growth conditions, blue light emitting diodes were created by changing only the distance d, and the relationship between distance and yield was investigated. As shown in Figure 6, when the distance d is 5 - or less, the yield is 70. Although the yield was approximately stable within the range of ~80%, when the distance d exceeded 3 sea breams, the yield decreased rapidly.

This is because when the distance d is less than 3, a grown layer with good crystallinity can be obtained with good reproducibility, whereas when the distance d exceeds 3, a grown layer with good crystallinity cannot be obtained with good reproducibility. This is because it cannot be done.

Furthermore, not only the distance d but also the temperature gradient is 3 to 15"C/a
Experiments were conducted with distance a varied within a range, and it was found that, regardless of the temperature gradient, the yield of blue light emitting diodes sharply decreases when distance d exceeds 3-.

(g) Effects of the Invention According to the method of the present invention, an 810 single crystal with good crystallinity can be grown with good reproducibility, so that the manufacturing yield of blue light emitting diodes and the like is improved.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the liquid phase epitaxial growth apparatus used for manufacturing Si0 single crystals, Figure 2 is a characteristic diagram showing the relationship between distance d and rocking curve width, and Figure 3 is a diagram showing the relationship between distance d and blue light emitting diode. FIG. 3 is a characteristic diagram showing the relationship with yield. (4) - Graphite crucible, +5) Si melt, +81
-8 i O single crystal substrate.

Claims (1)

[Claims] (1) When a SiC single crystal substrate is immersed in a Si melt in a graphite crucible and a SiC single crystal is grown on the substrate,
A method for liquid phase epitaxial growth of a SiC single crystal, characterized in that the distance between the substrate and the bottom surface of the crucible is less than or equal to mm.