Temperature dependence of the Fermi level in HgCdTe narrow-gap bulk films at different mercury vacancy concentrations

We calculate Fermi level position in bulk HgCdTe with cadmium fraction from 19 to 22% as a function of temperature for different concentrations of mercury vacancies forming double-charged acceptors with ionization energies of 11 and 21 meV for neutral and singly charged states respectively. The concentration of free carriers in the bands at different temperatures and the proportion of acceptor centres in different charge states are calculated as well. The results explain the fast temperature quenching of photoconductivity involving the vacancies states. It is also shown that in a p-type material conductivity dependence on temperature includes an exponential growth region with a characteristic energy much greater than a half of the bandgap at zero temperature expected for an intrinsic semiconductor. Keywords: narrow-gap semiconductors, HgCdTe, Fermi level, doubly charged acceptors.