Single-crystal – oriented-crystal – and epitaxy growth processes; – Processes of growth from solid or gel state
Reexamination Certificate
1999-10-20
2001-09-25
Kunemund, Robert (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Processes of growth from solid or gel state
C117S002000, C117S003000, C117S005000, C117S006000, C117S008000, C117S088000, C117S104000, C117S952000
Reexamination Certificate
active
06294016
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to a method for manufacturing a p-type GaN-based thin film using plasma nitridation together with rapid thermal annealing (hereinafter referred to as “RTA”), thereby providing high hole concentration for the thin film. Formation of p-type GaN-based thin films with high hole concentration is one of the most essential techniques in fabricating optoelectronic devices such as blue/white light emitting diodes (LEDs), laser diodes (LDs) and electronic devices which employ nitride semiconductors.
2. Description of the Prior Art
Reliable formation of high conductivity p-type GaN is one of the most demanding techniques in fabricating optoelectronic devices such as blue-green light emitting diodes (LEDs), blue laser diodes (LDs), and solar-blind ultraviolet photodetectors. For Mg-doped GaN grown by metalorganic chemical vapor deposition (MOCVD), however, it was difficult to obtain p-type conductivity due to the passivation by electrically inactive Mg—H complexes which are formed in the films by hydrogen from the growth ambient. To overcome this problem, a low energy electron beam irradiation [H. Amano el al., Jpn. J. Appl. Phys. 28, L2112 (1989)] or a RTA at 700° C. for 20 min in an N
2
ambient [S. Nakamura et al., Jpn. J. Appl. Phys. 31, L139 (1992)] has been commonly employed to dissociate hydrogen from the Mg—H complexes, giving rise to a p conduction with hole density in the low 10
17
cm
−3
range. Currently, RTA dominates over other treatments in activating the Mg acceptors. The problem has been intensified by the presence of compensating donor defects, e.g., the nitrogen vacancy whose formation is energetically favorable under p-type conditions. To date, the activation of the Mg acceptors in GaN thin films grown by a MOCVD process has been utterly dependent on such thermal treatments. However, the self-compensation can not be mastered by the post growth treatments and remains to be overcome to achieve hole concentration above mid-10
17
cm
−3
. In this regard, a new technique to further improve the p-conductivity is highly desired in the GaN-based III-nitride thin films.
SUMMARY OF THE INVENTION
The intensive and thorough research on the p-type GaN-based III-nitrides repeated by the present inventors, resulted in the finding that the combined treatment of nitrogen plasma irradiation (hereinafter referred to as “nitridation”) along with RTA annealing can better remove the hydrogen existing in the p-type GaN-based thin films compared with RTA treatment only, thus promote the activation of Mg acceptors from Mg—H complexes effectively.
Therefore, it is an object of the present invention to overcome the above problems encountered in prior arts and to provide a method for forming an enhanced p-type conductivity in GaN-based thin films which have low resistivity with high hole concentration.
In accordance with the present invention, the above objects could be accomplished by a provision of a method for forming a p-type GaN-based thin film, comprising the steps of: forming a thin GaN nucleation layer by use of a MOCVD process; growing the GaN-based epitaxial layer to a desired thickness while doping the epitaxial layer with magnesium, with hydrogen serving as carrier gas; subjecting the grown layer to nitridation and RTA treatment in combination.
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patent: 5306662 (1994-04-01), Nakamura et al.
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patent: 5766695 (1998-06-01), Nguyen et al.
patent: 6100174 (2000-08-01), Takatani
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Ahn Kwang Soon
Jang Ja Soon
Kim Sang Woo
Lee Ji Myon
Park Rae Man
Knobbe Martens Olson & Bear LLP
Kunemund Robert
Kwangju Institute of Science and Technology
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