The I-V characteristics of Aulsemi-insulating InP (100) under reversed bias have been measured between 230 K and '290 K. A simple model based on the thermionic field emission theory (TFE) is proposed to describe this system. Based on this model, the value of the bandgap obtained from the C V characteristics is in reasonable agreement with the literature. At room temperature, the corresponding fitted values of the barrier height Qb and the series bulk resistance R, are 0.68 0.05V and 1.32 x IO'R respectively.