Electrical conduction model for polycrystalline GaAs films

Abstract

An electrical conduction model for polycrystalline (PX) GaAs is presented to explain the electrical properties of this material. It is predicted that these properties cannot be explained without considering an additional rectangular potential barrier (qϕ) at the grain boundary and an additional mechanism of carrier transport (two-step tunneling process via grain boundary states) across the grain boundaries. It is demonstrated that the grain-boundary material in polycrystalline GaAs films is disordered in nature. Present computations have shown that the dependence of qϕ on doping density is very complicated and it is controlled by the processes of As clustering, and segregation of dopant as well as As atoms at the grain boundaries. It is also shown that the dopant segregation mechanism is present only in n-type PX-GaAs films, whereas it is absent in p-type samples. The dependence of carrier mobility and resistivity of this material on the doping density, temperature, and grain size has also been studied. A satisfactory agreement is observed between the theoretically computed results and available experimental data.