Electrical properties and thermal stability of ion beam deposited BN thin films

Boron nitride (BN) thin films were grown in UHV by alternating deposition of low energy mass separated B-11(+) and N-14(+) ions. Depending on the deposition conditions films are disordered (t-BN), hexagonal (h-BN) or cubic (c-BN). These films were annealed in various gas environments and characterized by infrared spectroscopy as a function of annealing temperature. Disordered BN films (t-BN) show a gradual structural change towards crystalline h-BN upon annealing, whereas for c-BN films only relaxation of compressive stress is observed. c-BN films are stable up to 1200 K for annealing in air. Electrical measurements on various BN-films deposited on metal and silicon substrates reveal Frenkel-Poole emission as the dominant conduction mechanism at high bias voltages. The current-voltage characteristics of BN/Si heterojunctions, studied between room temperature and 500 K, are almost symmetric, i.e. do not show significant rectifying behavior. Current-voltage curves were found to be reversible in temperature but we find irreversible behavior after applying high bias voltages. (C) 1997 Elsevier Science S.A.