1. Field of the Invention
The present invention relates to a method of growing single crystal Gallium Nitride (GaN), particularly to a method of growing single crystal Gallium Nitride (GaN) on silicon substrate.
2. Description of Related Art
Due to rapid advance of researching and fabrication of ultraviolet to blue optoelectronic elements, such as blue light emitting diode, blue LASER semiconductor, ultraviolet sensor, GaN has been one of the most important wide-band-gap semiconductor materials in group III nitride. At the present, GaN grows on sapphire or silicon carbide substrates, however those two substrates are expensive, and it is not easy to integrate with silicon s miconductor which is mature and cheap, and consequently the market growth of those two technology is retarded. Owing to wide application range, mature and cheap silicon technology, advantage and potential of growing GaN elements on silicon wafer is expected. It is best to grow GaN film on GaN substrate, but it is regrettable that GaN substrate of large area (over two inch in diameter) and low defects is still under research, therefore to find another substrate materials is necessary. Substrate used most frequently for the time being is sapphire. Owing to 16% lattice mismatch between sapphire and GaN, it is difficult to achieve high quality GaN buffer layer. Silicon carbide is another potential substrate material, because of its only 3% lattice mismatch between SiC and GaN, good electric and thermal conductivity, but it is very expensive, and not suitable to commercialize. As a result, to find a technology is valuable of growing substrate which has low lattice mismatch with GaN, good electric and thermal conductivity, low price. Owing to wide application range, mature and cheap silicon technology, growing GaN elements on silicon wafer has its advantage and potential. However, grow directly GaN on silicon wafer will results in high density of defects and cracks, and consequently the hetero-structure eptiaxy technology is retarded.