Capacitance‐voltage measurements on GaAs metal insulator semiconductor structures are plagued by charging problems. Additionally, it seems that accumulation cannot be reached owing to Fermi‐level pinning and consequently the insulator capacitance cannot be determined. Furthermore, it is difficult to determine semiconductor characteristics in these MIS structures, which may have changed during annealing. In this paper, a measurement technique is described which eliminates the effect of the charging, allowing the measurement of insulator capacitance, surface potential, and semiconductor doping. This measurement technique is based on the study of transient photovoltage, transient capacitance, and the charging characteristics. This new measurement technique is used to evaluate GaAs MIS diodes and test results are presented.