Schottky junction properties on high quality boron-doped homoepitaxial diamond thin films

Experiments of annealing effect of boron-doped homoepitaxial diamond film on Schottky junction properties have been conducted to investigate the origin of the “pinning” states in oxidized surface of diamond. Metals of Al, Ni, Au, and Pt are evaporated onto boron-doped diamond films with post thermal annealing less than 800 °C or higher than 900 °C. The current–voltage (I–V) characteristics of Schottky junctions for low-temperature annealing show excellent rectification behavior, indicating the existence of the “pinning” states. After high-temperature annealing, the I–V curves show worse rectification or ohmic properties depending on the metal work function, suggesting the decrement of the density of “pinning” state. Capacitance–voltage measurements for the Schottky diodes show the strong thermal annealing effects on surface region property of the diamond film only after high temperature annealing. A possible explanation is the oxygen-related “pinning” states existing in the oxidized-surface of diamond are annealed out partially during high temperature annealing.