| 摘要 |
Refractory, eg quartz, vessels are coated with a thin layer of boron nitride, such that the vessels may be repeatedly used as containers for the growth of high purity gallium arsenide crystal. The boron nitride coating prevents the incorporation of silicon, as well as other impurities, within the crystal. The boron nitride coating may be applied either by chemical vapour deposition or plasma spraying. In chemical vapour deposition, a gaseous active nitrogen compound and a gaseous boron-containing compound are passed over the vessel within a heated deposition reactor. Suitable reactants as the nitrogen compound are (CH3CH2)3N, NH3 whilst as the borin-containing compound BCl3, (CH3CH2)3N:BH3, B2H6 may be used. In the plasma spraying embodiment boron nitride particles of approximately 325 mesh into said plasma spray and repeatedly spraying the quartz vessel so as to develop a boron nitride coating of 3 to 5 microns. The method of growing gallium arsenide crystals within a boron nitride coated boat comprises:- a) filling the hot end of the boat with pre-melted gallium arsenide; b) supporting a gallium arsenide seed crystal at cold end of said boat; c) placing said boat within a vacuum furnace; d) sealing said furnace, while drawing a vacuum; e) maintaining a cold zone within the furnace at the arsenic boiling point while gradiently heating the boat, such that the gallium arsenide at the hot end is maintained is maintained in the molten state at approximately 1255 DEG C and the gallium arsenide seed at the cold end remains solid at approximately 1237 DEG C, and f) gradually freezing the molten gallium arsenide. This method is illustrated in Fig. 2 where the BN coated boat 40 is filled with GaAS together with a seed crystal 52, inserted into a quartz tube 42 which is placed inside a furnace. <IMAGE> |
