Evaluation of Surface Recombination Velocity on CdTe Radiation Detectors by Time-of-Flight Measurements

The surface recombination velocity on high-resistivity CdTe with several different crystallographic orientations-(111), 5deg off from (111), 8deg off from (311), and (511)-has been investigated by using a ldquomutau-modelrdquo spectral fitting method in combination with time-of-flight drift mobility measurement. In the samples orientated parallel to (111) and 5deg off from (111), the Cd face exhibits a higher surface recombination velocity ( ~ 6 times 10⁵ cm/s) than the Te face ( ~ 3 times 10⁵ cm/s). Away from the polar face and toward the (511) face, the difference is less pronounced, although not completely absent.