Evaluation of surface recombination velocity of CdTe radiation detectors by time-of-flight measurements

The surface recombination velocity of high resistivity CdTe with several different crystallographic orientations of (111), 5° off from (111), 8° off from (311) and (511) has been investigated by using a combination of a “μτ-model” spectral fitting method and a time-of-flight drift mobility measurement. In the (111) and the 5° off from (111) samples, the Cd face shows higher surface recombination velocity (∼6 × 10⁵ cm/s) than that of the Te face (∼3 × 10⁵ cm/s). Away from the polar face toward the (511) face, the difference is less pronounced although not disappeared completely.