Epitaxial Growth of Zinc‐ and Cadmium‐Doped Gallium Phosphide by Gallium Chloride Vapor Transport

Zinc‐and cadmium‐doped gallium phosphide crystals have been grown by an open tube halogen transport process at 805°–875°C. The zinc‐doping varied from 10¹⁷ to 10¹⁹ cm⁻³ while cadmium could be incorporated at levels ranging from 10¹⁶ to 10¹⁸ cm⁻³. We observed a linear dependence of zinc and cadmium concentration on the partial pressure of the dopant in the growth ambient. This linear dependence is evidence for a nonequilibrium, kinetically controlled process. The structural and electrical properties are compared with the properties of crystals grown by the wet hydrogen process. A study of the gallium consumption as a function of experimental variables yielded a Ga to ratio of , independent of feed rate and carrier gas flow. A ratio of 2.64 is predicted from thermodynamic data provided the species can be neglected in the initial reaction between and Ga.