Effect of deviations from the stoichiometric composition on the electrical and photoelectrical properties of the Hg$_3$In$_2$Te$_6$ compound

The results of studying the electrical and photoelectric properties of Hg$_3$In$_2$Te$_6$ bulk crystals with stoichiometric composition and of Hg$_{3(1+\delta)}$In$_{2(1-\delta)}$Te$_6$ crystals with a deviation from the stoichiometric composition of $\delta$ = $\pm$ 0.06 are reported. It is shown that variations in the ratio between the Hg and In components in the crystals yield an increase in the concentration of mutually compensating donors and acceptors which barely affect the position of the donor level in the band gap (the level energy is $E_D=E_c$ – (0.18 $\pm$ 0.02) eV, but determine the photoconductivity spectrum near the fundamental absorption edge. An expression for the wavelength dependence of the photocurrent and the parameters of nonequilibrium charge carriers are presented to describe the experimental data.