Synthesis of Gallium Phosphide

An open‐flow synthesis system for the production of polycrystalline , using flowing over Ga in a temperature gradient, has been investigated with regard to purity of the product and yield of in terms of the elements Ga and P. This material is suitable as starting material for single‐crystal growth by the liquid‐encapsulated Czochralski technique. Optimization of the synthesis time, flow rate, and temperature gradient resulted in a P reaction efficiency of 50–55% and a yield of 35–38g per 50g of Ga. A mechanism involving the formation of a reaction barrier over the Ga was used to explain the increase in P reaction efficiency and yield with decreasing flow rate. Both an increased reaction efficiency and yield were observed with increasing temperature gradients, indicating a diffusion‐controlled reaction. It was found that Si atoms cm⁻³ were incorporated in the when pyrolytic boron nitride boats and silica liners were used. When He was substituted for H₂ as the carrier gas, the Si contamination dropped to about cm⁻³. Silicon contamination of about atoms cm⁻³ was observed using an all silica system. When water vapor was introduced in small amounts to He in the pyrolytic boron system, the yield was reduced by about 10% but the material produced was found to have an optically active Si content of about 10¹⁶ cm⁻³. These results indicate the dominance of the vapor transport mechanism for Si contamination of . Material grown in an all‐pyrolytic boron nitride system, where the boats were physically separated from hot silica, had a Si contamination of less than  cm⁻³.