Photoconductivity spectroscopy of arsenic-related acceptors in HgCdTe

The arsenic impurity is widely considered to be the best choice for p-type doping of HgCdTe ternary alloys, which has been a formidable problem for decades. This work studies the terahertz photoconductivity of Hg1-x Cd (x) Te with x similar to 0.22 doped with arsenic and subjected to activation annealing to obtain p-type conductivity. In addition to the inevitable photoexcitation lines of mercury vacancies, which act as double acceptors, the spectra contain a distinctive line associated with the photoexcitation of the arsenic-related acceptor. In contrast to the predictions of the effective mass approximation, the binding energy of the acceptor is found to be about 25 meV. The possible reasons for this unexpectedly high chemical shift, which is not quite consistent with the data recently obtained from photoluminescence and Hall effect measurements, are discussed.