| 摘要 |
PROBLEM TO BE SOLVED: To reduce the crystal defects and cracks (mechanical breakdown) caused by the crystal-lattice mismatching of a GaN or AlGaN epitaxial crystal to a crystal substrate using a SiC crystal, a sapphire crystal or a silicon crystal; to improve the characteristic of a device using these crystals. SOLUTION: A BP (boron phosphide) crystal (cubic crystal structure) layer is so formed between a silicon crystal substrate and a GaN or AlGaN epitaxial operational layer, and further, a GaN/AlN superlattice structure layer is so formed on the buffer layer as to take continuously a GaN or AlGaN operational crystal layer structure. Thereby, the crystal defects to the operational layer can be reduced, As a result, the device characteristics including primarily the high-frequency characteristic of the device can be improved largely. Also, by growing selectively the GaN or AlGaN operational crystal layer only to the operational-layer portion of the silicon crystal substrate, the crystal defects to the operational layer can be reduced. Also, the warp of the crystal substrate caused by the interface stress can be prevented between the substrate crystal and the epitaxial crystal which is generated after the growth of the epitaxial crystal. COPYRIGHT: (C)2005,JPO&NCIPI
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