The growth of boron monophosphide crystals by chemical transport

Abstract

The crystal growth of boron phosphide, BP, has been investigated by using the closed-tube chemical transport of polycrystalline material, prepared by the hydrogen reduction of a boron tribromide-phosphorus trichloride mixture. Experimental parameters including the nature of the transport agent, source temperature, temperature gradient, and surface condition of the reaction tube, were studied. Using iodine or bromine as a transport agent and a source temperature of 1270–1290 °C, single crystals of boron phosphide, identified by the X-ray diffraction method, were obtained in the form of polyhedra with well-defined faces. Molten potassium hydroxide or a molten mixture of sodium hydroxide-sodium peroxide were used as an etchant to reveal structure defects in boron phosphide crystals. The transported boron phosphide crystals were p-type with a room temperature resistivity of approximately 0.5 ohm-cm. Resistivity measurements in the temperature range 77–350 °K indicated the presence of two impurity states with activation energies of approximately 0.009 and 0.052 eV, respectively. In spite of the high impurity concentrations, the transported crystals are suitable as substrates for the epitaxial growth of boron phosphide.