Refractory semiconductor of boron phosphide

Abstract

The single crystal growth of boron phosphide (BP) by employing the high pressure flux method and chemical vapor deposition (CVD) process is described together with characterization of the prepared BP and its electrical, thermal, semiconducting, and electrochemical properties. BP single crystals prepared by the high pressure flux method contain copper used as the flux, but they are promising for photocathode materials. BP single crystalline wafers prepared by the CVD process using Si wafer substrate contained autodoped silicon with the concentration of 1018−1020 atoms·cm−3, depending on the growth temperature and the substrate plane. The Si atoms which act as acceptors are incorporated at phosphorus sites in BP. The lattice constants determined by the Bond method explain the conduction type of BP. Some electronic transport properties such as donor and acceptor levels and lattice scattering process before and after thermal neutron experiments are clarified. The thermal conduction is limited by three-phonon processes. The formation of defects by thermal neutron irradiation and that of structural disorder by ion-irradiation are mentioned. Schottky diodes consisting of n–BP and Sb or n–BP and Au, which are denoted as n–BP–Sb and –Au, respectively, show excellent characteristics, and their barrier heights are independent of metals and two-thirds of energy bandgap, expected from the surface-state model. Finally, recent results on thermoelectric properties of sintered specimens are mentioned.