Influence of resonant defect states on subband structures in Hg1−xCdxTe

Abstract

A revised C–V fitting model is presented to determine the subband structures of n-type inversion layer in p-type Hg1−xCdxTe with higher native doping concentration by taking into account the influence of a resonant defect level, which is found from the capacitance measurements. By the model the subband structure and its dependence on surface electron concentrations Ns as well as the relationship between the subband structures and doping concentrations for Hg1−xCdxTe with x=0.21 and a wide doping range of NA = 3.6 × 1016–6.95 × 1017 cm−3 are obtained. By the C–V fitting procedure the resonant defect level, which is located at 45 meV above the conduction band edge for the samples of x=0.21, and its density are also obtained. The annealing and Au-doping experiments on the sample as well as the theoretical analysis reveal that the resonant defect states arise from mercury vacancies occupied by oxygen atoms. The way to eliminate the defect states is also discussed.