Transport properties of n-type CuGaSe2

Hall effect, electrical conductivity, and charge carrier mobility of n-type CuGaSe2 single crystals are studied in the temperature range between 2 and 300 K. The experimental data, analyzed within the framework of a simple model of a semiconductor with two types of carriers of one sign, indicate the existence of an impurity band. The values of the gap between the main and impurity band, the concentration of donors, and the concentration of the compensating acceptors are calculated. The mobility above 100 K is described by scattering of conduction band electrons at phonons and impurities. The sharp drop at low temperatures is explained by a crossover to Mott-type variable-range hopping in the impurity band.