Dependence of carrier mobility on an electric field in gallium selenide crystals

The dependence of the mobility of charge carriers on voltage has been studied in undoped GaSe single crystals and crystals doped with gadolinium; the latter crystals have exhibited various values of dark resistivity ($\rho_{\mathrm{d.r.}}\approx$ 10$^4$–10$^8$ $\Omega$ cm at 77 K) and of the doping level ($N$ = 10$^{-5}$, 10$^{-4}$, 10$^{-3}$, 10$^{-2}$, and 10$^{-1}$ at%). It is established that the dependence of the charge-carrier mobility on the electric field applied to the sample $E\le$ 10$^2$ V/cm is observed in undoped high-resistivity GaSe crystals ($\rho_{\mathrm{d.r.}}\ge$ 10$^4$ $\Omega$ cm) and in lightly doped GaSe crystals ($N\le$ 10$^{-2}$ at%) in the region of $T\le$ 150 K. It is found that this dependence is not related to heating of the charge carriers by an electric field; rather, it is caused by elimination of drift barriers as a result of injection.