JPS6048900B2 - Gallium arsenide crystal growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for vapor phase growth of gallium arsenide by an open tube method using a disproportionation reaction of arsenic chloride-gallium-hydrogen system, which produces a crystal layer having a high specific resistance and a crystal layer having a low specific resistance. The present invention relates to a method for continuously growing layers of crystals having .

Gallium arsenide crystals used as microwave direct oscillation devices and other microwave devices are usually grown by a vapor phase epitaxial method or a liquid phase epitaxial method.

Since the vapor phase epitaxial method allows relatively easy control of the thickness of the epitaxial layer, it is particularly suitable for growing crystals used in the manufacture of field effect transistors. The crystal used to produce the electrolytic effect of gallium arsenide usually has a resistivity of 1.
A buffer layer with a specific resistance of 20Ωa or more is formed by an epitaxial method on a semi-insulating substrate with a resistivity of 20Ω or more, and a buffer layer with a specific resistance of 0.0a or more is further formed on the semi-insulating substrate by an epitaxial method.
An n-type active layer with a resistance of 5 Ωa or less is grown to a thickness of 1 μm or less.

An example of a conventional method of growing this crystal layer by a vapor phase growth method using a disproportionation reaction of Ξarsenic chloride-gallium-hydrogen will be explained with reference to FIG. Gallium 11, the surface of which is completely covered with gallium arsenide, is maintained at 850° C. with a temperature distribution that uniformly heats the entire surface.

Then, the temperature inside the reaction tube decreases monotonically from the position of gallium 11 toward the gallium arsenide substrate 12 located downstream, and the temperature at the position of the substrate 12 reaches 750°C and 0.5°C/C! Set the temperature gradient of Tl. Until the temperature reaches the above set value, 150cc/mi is applied from each gas inlet 13 and 14.
n) 100 cc/min of hydrogen gas was allowed to flow into the reaction tube, and when the above set value was reached, hydrogen passed through 3 arsenic chloride kept at 25°C was passed through the gas inlet 13, and 10~ 2. Grow a buffer layer. At this time, the growth rate of the buffer layer was 0.3 to 0.4 μm/min,
The buffer layer can have a carrier concentration of 5×10″00−0 or less and a specific resistance of 20Ωα or more.i After growing the buffer layer in the above conditions, trichloride was heated at 5°C through the gas inlet 13. A working layer is grown by passing hydrogen passed through arsenic and at the same time flowing hydrogen containing hydrogen sulfide at a mole fraction of 1×10 −° from the gas inlet 14 .

At this time, the growth rate of the active layer can be set to 0.2 μm/Min or less, and the active layer becomes n-type, and its specific resistance is 0.
．． 01Ωα. In FIG. 1, 15 is a substrate support stand, 16 is a reaction tube, 17 is a gas outlet, and 18 is a quartz board. However, in this epitaxial growth method, the growth rate changes greatly between the initial and final stages of growing the active layer, making it difficult to control the thickness of the active layer, and furthermore, the resistivity within the active layer is low near the surface. It changes greatly near the interface with the buffer layer.

Another method is to heat iron to a desired temperature, react it with hydrochloric acid, feed it into a reaction tube, and dope it into a crystal layer grown by an epitaxial method to obtain a buffer layer.

However, in the above growth method, a furnace for heating the iron must be added to a normal vapor phase growth apparatus, and there is also a possibility that iron may be mixed into the active layer. The present invention solves these drawbacks by simply stopping the flow of the dopant gas into the reaction tube when the position of the substrate is changed from among the growth conditions for growing a normal operating layer. This is a method in which a layer having a high specific resistance is grown, and will be explained in detail below. FIG. 2 shows an example of the present invention, in which (a) is a cross-sectional view inside the reaction tube, and (b) is a diagram showing the temperature distribution inside the reaction tube.

21 is a reaction tube for growth, 22 is a tube for supplying hydrogen, which is made by passing arsenic trichloride through gallium 23- whose surface is completely covered with gallium arsenide, into the reaction tube, and 24 is a gas to be a dopant. This is a tube for supplying gas to the reaction tube so as not to mix it into the gallium 23, and 25 is an outlet for discharging gas from the reaction tube.

Further, 26 is a substrate for epitaxial growth. In FIG. 2, 27 is a substrate support stand, and 28 is a quartz board.

The gallium 23 whose surface is completely covered with gallium arsenide is located at a position 31 having a uniform temperature of 850° C., and two positions 32 and 33 are provided as positions for placing the l-substrate 26.

At positions 32 and 33, the temperature is set at 750°C, and the temperature gradient is set in the range of 0.1°C/An to 5°C/Cm, with the temperature decreasing from upstream to downstream. Furthermore, the temperature between position 32 and position 33 is 2°C higher than that at position 33.
Provide a section that is ~10°C lower. The substrate 26 was placed at a position 33, and hydrogen passed through Ξ arsenic chloride kept at 10° C. was flowed through the gas inlet 22 at a flow rate of 150 cc/min, and hydrogen was flowed through the gas inlet 24 at a flow rate of 100 cc/min. Flow.

In this case, position 31 where gallium is placed and position 3 where the substrate is placed.
Since there is a lower temperature area between the positions 33 and 3 where the substrate 26 is placed, the difference between the acceptor atoms in the crystal layer growing on the substrate 26 and the donor atoms is kept below 10"°. The specific resistance of this crystal layer is 50Ωα
It is possible to do more than that. Next, the support rod 2 of the board 26
7 forward, the board 26 is moved to position 3.
Move to 2. At the same time, when hydrogen sulfide is grown at a mole fraction of 1.5 x 10-° from the gas inlet 24, the specific resistance becomes 0 at a growth rate of 0.2 μm/min.
．． An n-type operating layer of 01Ωα can be obtained. This phenomenon can be qualitatively explained as follows.

If there is no position between the gallium placement position 31 and the substrate placement position 33 where the temperature is lower than the substrate placement position 33, the vapor pressure PAS of silicon and the gallium vapor pressure PAS in the atmosphere at the substrate placement position 33 do not exist. Ratio PAs of vapor pressure PGa
/PCa maintains a value smaller than 1 but above a certain level. Therefore, if we grow a crystalline layer without doping, we will obtain an n-type crystalline layer with a donor atomic concentration minus an acceptor concentration, that is, a carrier concentration of 10"° α-° or more. However, if gallium is Position 33 where the board is placed between position 31 where the board is placed and position 33 where the board is placed
If a lower temperature region exists, approximately equal numbers of gallium atoms and silicon atoms will be deposited in the reaction tube as gallium arsenide in this lower temperature region.

Therefore, in the atmosphere at the position 33 where the substrate 26 is placed, PAs/Pca becomes smaller than the above-described certain value. Therefore, in the growing crystal layer, the donor atom concentration decreases and the acceptor atom concentration increases, resulting in an n-type crystal layer or a P-type crystal layer with a carrier concentration of 10" cm -3 or less. If a portion between position 32 and position 33 where the temperature is 2°C to 10°C lower than position 33 is appropriately set, a crystal having a carrier concentration of 10″°α-° or less can be obtained. As explained above, in the first embodiment, without changing the flow rate of hydrogen or the temperature of Ξ arsenic chloride contained in hydrogen,
When the carrier concentration is 101゜'-゜ or less, the specific resistance is 50Ωa.
The above buffer layer can be formed, and an n-type active layer can be formed thereon using the same thermal cycle as that used to form the high resistivity buffer layer. In vapor phase epitaxial crystal growth, the present invention makes it possible to continuously grow a layer with a high resistivity of 50Ωα or more and an n-type layer with a low resistivity of 1Ωa or less by simply changing the position of the substrate during growth. Its advantages allow it to be used in growing epitaxial crystals used in the fabrication of gallium arsenide field-effect transistors and planar Gunn diodes.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the inside of a reaction tube for vapor phase epitaxial growth of gallium arsenide in a conventional Ξ arsenic chloride-gallium-hydrogen system, and FIG. FIG. 2b is a cross-sectional view of a reaction tube for gas phase epitaxial use, and FIG. 2b is a temperature distribution diagram inside the reaction tube of FIG. 2a. 21...Reaction tube, 22, 24...Gas inlet, 25...Gas outlet, 28...
・Quartz board, 23...Gallium, 26...
...Substrate, 27...Support rod for the board, 31...
...Position to place gallium, 32, 33...
Where to place the board.

Claims (1)

[Claims] 1. In a gallium arsenide vapor phase growth method using an open tube method using an arsenic trichloride-gallium-hydrogen system disproportionation reaction,
Two growth regions where the temperature decreases downstream from the gallium side are set, and the temperature at the position where the gallium is placed is equalized.
The temperature distribution from downstream of the location where gallium is placed to the growth region closer to the gallium is monotonically decreased, and a region with a lower temperature than the two growth regions is provided between the two growth regions, thereby changing the position of the substrate during epitaxial growth. A method for growing gallium arsenide crystals, characterized in that crystal layers having different resistivities are successively grown by moving the gallium arsenide from one position to the other.