| 摘要 |
Crystalline boron phosphide is prepared by contacting phosphorus vapour with boron phosphide at a first region in a reaction system, passing the gas thereby formed to a second region in the system where crystalline boron phosphide is deposited from the gas phase, the temperature at the first region being at least 530 DEG C., the temperature at the second region being lower than that of the first region, and the temperature difference between the two regions being at least 30 DEG C. The process may be carried out in an open, partially closed or completely closed reaction system. If an open system is used, phosphorus vapour can be passed over the boron phosphide by means of an inert carrier gas, e.g. helium. In a partially closed system, phosphorus vapour is drawn over the boron phosphide by means of pump suction. Doping substances may be mixed with the phosphorus vapour or boron phosphide starting material to produce crystalline boron phosphide of a prescribed conductivity. The process may be repeated using different doping substances to produce boron phosphide monocrystals having layers of diffferent conductivity. In an example, polycrystalline boron phosphide and red phosphorus were placed in separate alumina boats at each end of an open alumina tube. The phosphorus was heated to 400 DEG C. and the boron phosphide to 1500 DEG C. Helium was passed through the tube such that monocrystalline boron phosphide was deposited on the walls of the tube, see Fig. 1 (not shown). The crystals were removed mechanically or by treatment of the tube walls with HF. |
