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 805~176 The zinc-doping varied from 10 I7 to 10 TM cm-3 while cadmium could be incorporated at levels ranging from 10 TM to 10 TM cm-3. We observed a linear dependence of zinc and cadmium concentration on the partial pressure of the dopant in the growth ambient. This l inear dependence is evidence for a nonequil ibrium, 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 gall ium consumption as a function of experimental variables yielded a Ga to PCI3 ratio of 2.5 _ 0.2, independent of PC13 feed rate and carrier gas flow. A ratio of 2.64 is predicted from thermodynamic data provided the species GaC12 (g) can be neglected in the initial reaction between HC1 and Ga. At the present ime the open tube vapor transport technique used to produce large single crystals o