We present a physical model to study the interface states in p‐n heterostructures at different ambient temperatures. Field‐assisted emission of such states is considered as the source for the linear increase in charge concentration at the p‐n interface with the applied reverse voltage. The high frequency capacitance‐voltage technique is used to study the charging and discharging of interface states in an MBE‐made sample at different temperatures and different biases. The experimental results show good agreement with the prediction of our model. ©1995 American Institute of Physics.