Single-crystal – oriented-crystal – and epitaxy growth processes; – Processes of growth from liquid or supercritical state – Havin growth from molten state
Reexamination Certificate
1999-07-07
2001-12-04
Kunemund, Robert (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Processes of growth from liquid or supercritical state
Havin growth from molten state
C117S083000, C117S084000, C117S956000, C252S0623GA
Reexamination Certificate
active
06325849
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a P-type GaAs single crystal having low dislocation, and a manufacturing method therefor.
2. Related Arts
P-type GaAs single crystals have been widely used as sliced and epitaxially grown for use in manufacturing a compound semiconductor laser or a light-emitting diode (LED).
It is well known that the P-type GaAs single crystals widely used for compound semiconductor lasers and LEDs can be manufactured using various methods, such as the horizontal Bridgman (HB) method, the horizontal gradient freeze (GF) method, the liquid encapsulated crystal growth (LEC) method, the vertical Bridgman (VB) method, and the vertical gradient freeze (VGF) method.
Since high light emission efficiency and long service life are requisite qualities for a compound semiconductor laser, a P-type GaAs single crystal having a lower dislocation density is required. Therefore, generally, the horizontal Bridgman (HB) method, the gradient freeze (GF) method, the vertical Bridgman (VB) method, or the vertical gradient freeze (VGF) method is employed to manufacture a P-type GaAs single crystal.
However, when using any of these methods, the average dislocation density is equal to or greater than 1000 cm
−2
, and it is difficult to obtain a high yield when manufacturing P-type GaAs single crystals having an average dislocation density of 500 cm
−2
or lower.
On the contrary, it is known that doping a crystal with S and Si can effectively reduce dislocation, However, in this case, only an N-type GaAs single crystal is obtained.
As example means for resolving the above shortcomings, doping GaAs crystal with Zn and S using the horizontal Bridgman (HB) method is described in Japanese Unexamined Patent Publication No. Sho 63-57079. However, although a P-type GaAs single crystal having an average dislocation density of 1000 cm
−2
or lower can be obtained using this method, it is difficult to manufacture a P-type GaAs single crystal having an average dislocation density of 500 cm
−2
.
It has been reported that In, which is a neutral impurity, can contribute to the reduction of the dislocation of GaAs crystal (Proc. 12th Intern. Symp. on GaAs and Related Compounds, London-Bristol, 1986, p. 7-2). As related in this report, a 2-inch GaAs wafer which was doped with Zn, at a density of 1.5×10
19
cm
−3
, and In, at a density of 4.0×10
19
cm
−3
, served as a semiconductor wafer having no dislocation.
However, since the segregation coefficient of In is small, i.e., 0.1, in order to perform the high density doping of a crystal with In, a single crystal must be manufactured from melt-GaAs to which a large amount of In has been added in advance. However, if a crystal is manufactured under these conditions, cell growth is begun due to constitutional supercooling during the solidifying of the crystal, and there is a considerable reduction in productivity.
SUMMARY OF THE INVENTION
It is, therefore, one objective of the present invention to provide a P-type GaAs single crystal which resolves the conventional problems, and a manufacturing method therefor.
It is another objective of the present invention to provide a P-type GaAs single crystal having an average dislocation density of 500 cm
−2
.
To achieve the above objectives, according to the present invention, provided is a P-type GaAs single crystal containing Si and a P-type indicative dopant at an atomic ratio, for said P-type indicative dopant to Si, of 1.5 to 200, or preferably 2 to 100.
Further, relative to Si, B and/or S is contained as a dopant at an atomic ratio of 0.001 to 1000. Therefore, since the contained dopant has an atomic concentration of 1×10
17
to 1×10
20
cm
−3
, a P-type GaAs single crystal having a lower dislocation can be obtained.
In addition, a carrier concentration is 1×10
18
to 5×10
19
cm
−3
.
The average dislocation density of such a P-type GaAs single crystal can be equal to or lower than 500 cm
−2
.
Furthermore, at least one part of the Si can be replaced by Se and/or Te.
The doping method is not limited to the use of any of the above dopants. A doping source can be, for example, a metal, a compound, an oxide, or an impurity in polycrystal or in a container, and can take the form of a solid, a liquid or a gas.
To manufacture the above described P-type GaAs single crystal, an Si dopant and a P-type indicative dopant for a P-type GaAs single crystal are respectively loaded in a deposition container at a density of from 1×10
17
to 5×10
19
cm
−3
and at a density of from 1×10
18
to 5×10
20
cm
−3
, so that the atomic ratio of the P-type indicative dopant relative to Si ranges from greater than 1 to equal to or smaller than 1000, in particular, 1.1 to 500. Thus, the horizontal boat growth method or the vertical boat growth method can be employed.
Other features and effects of the present invention will become apparent during the course of the descriptions given for the following embodiments of the present invention.
REFERENCES:
patent: 5376583 (1994-12-01), Northrup et al.
patent: 5436194 (1995-07-01), Kondo et al.
patent: 6072817 (2000-06-01), Adachi et al.
patent: 6081541 (2000-06-01), Adachi et al.
European Search Report dated Oct. 15, 1999.
Patent Abstract of Japan: Pub. No. 58176200; Pub. Date: Oct. 15, 1983.
“Low Dislocation Density 3-inch Si doped GaAs Crystals by Vertical Boat Growth”, Y. Hagi, et al. Semiconducting and Insulating Materials 1996. Proceedings of the 9T Conference (SIMC), Apr. 29-May 3, 1996, pp. 279-282.
Patent Abstract of Japan: Pub. No. 59137400; Pub. Date: Aug. 7, 1984.
Patent Abstract of Japan: Pub. No. 04139098; Pub. Date: May 13, 1992.
Patent Abstract of Japan: Pub. No. 61136997; Pub. Date: Jun. 24, 1986.
DE 40 21 252 A (Hitachi Cable) Jan. 9, 1992. In German, with no Translation.
DE 196 38 583 A (Kernforschungsanlage Juelich) Apr. 2, 1998. In German with no translation.
Hideo Fujisawa
Kizuku Katano
Osamu Yamamoto
Alexander John B.
Conlin David G.
Dike Bronstein Roberts & Cushman IP Group
Kunemund Robert
Mitsubishi Chemical Corporation
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