Impurity-band transport near the metal–insulator transition in ZnSe epilayers grown by molecular beam epitaxy

Abstract

Electrical transport is studied in a number of ZnSe epilayers with donor concentrations in the range 1–3×1017 cm−3. Hall effect data are taken over the temperature range 10–300 K, and magnetoresistance data over the range 10–50 K. Transport is shown to be consistent with a two-carrier model, the second species being identified with transport in an impurity band distinct from the conduction band. At low temperature, the conductivity σ exhibits a log σ∝−(T0/T)1/4 behavior, and the samples show negative magnetoresistance. Moreover, both the parameter T0 and the magnetoresistance tend toward zero as the dopant concentration increases toward that of the metal–insulator transition.