Determination of the parameters of semiconducting CdF₂:In with Schottky barriers from radio-frequency measurements

Physical properties of semiconducting CdF₂ crystals doped with In are determined from measurements of the radio-frequency response of a sample with Schottky barriers at frequencies 10-10⁶ Hz. The dielectric constant, the dc conductivity, the activation energy of the amphoteric impurity, and the total concentration of the active In ions in CdF₂ are found through an equivalent-circuit analysis of the frequency dependencies of the sample complex impedance at temperatures from 20 to 300 K. Kinetic coefficients determining the thermally induced transitions between the deep and the shallow states of the In impurity and the barrier height between these states are obtained from the time-dependent radio-frequency response after illumination of the material. The results on the low-frequency conductivity in CdF₂:In are compared with submillimeter (10¹¹-10¹² Hz) measurements and with room-temperature infrared measurements of undoped CdF₂. The low-frequency impedance measurements of semiconductor samples with Schottky barriers are shown to be a good tool for investigation of the physical properties of semiconductors.