Electrical fluctuations in HgCdTe introduced during quenching after annealing

Abstract

HgCdTe epilayers used in infrared detectors have to be quenched after annealing in order to control the p-type carrier concentrations. It was found that μm-scale electrical fluctuations are introduced in the epilayer and around threading dislocation clusters during the quenching. Differential Hall measurements revealed an n-type region in the first 1 μm of the epilayer, followed by the p +-type (10 17 cm −3) region which gradually decreases with depth to 10 16 cm −3 in the next 5 μm. The fluctuating layer thickness decreased when the cooling rates increased. LBIC (laser-beam-induced current) images showed that p +-type electrical fluctuations and their dependence on the cooling rates are also observed around the threading dislocation clusters. The fluctuations are more than five times deeper than the former surface fluctuations. Simple estimations for the cooling process of the epilayers can qualitatively explain the experimental results.