Abstract
A new method is proposed to determine the photoionization threshold energy of a deep level from the dependence of photocapacitance on the scanning rate of light wavelengths. The validity is demonstrated by applying this method to minority carrier traps in an n‐type GaAs and a p‐type GaP. It is shown that Lucovsky's model of photoionization cross section is valid at least in photon energies less than 1.5 times the threshold energy.