Effects of temperature and rare-earth doping on the transport properties of GaSe crystals

Transport properties (electrical conductivity and Hall coefficient) of pure (nominally undoped) and rare-earth-doped (up to 10−1 at % holmium, gadolinium, and dysprosium) gallium monoselenide crystals have been studied in the temperature range 77–600 K. The results demonstrate that, at low temperatures, the Hall coefficient of both the undoped and doped crystals is temperature-independent, whereas their dark conductivity and carrier mobility exhibit Arrhenius behavior. The undoped and rare-earth-doped crystals differ markedly in dark conductivity and carrier mobility. The chemical nature of the dopants has no effect on the transport properties of the crystals, which depend only on the doping level. The observed anomalies can be accounted for by the presence of random drift barriers in the empty energy bands of the gallium selenide crystals.