Electric-field effect on the electrical conductivity of InSe and InSe〈Dy〉 crystals

Abstract

We have studied the effect of external dc electric field on the dark conductivity $\left( {\sigma _{d_0 } } \right)$ of undoped and dysprosium-doped InSe single crystals having different initial dark conductivities ($\sigma _{d_0 } = 2.5 \times 10^{ - 8}$ to 10⁻² S/cm at 77 K) and doping levels (∼10⁻⁵ to 10⁻¹ at % Dy, respectively). At T ≤ 200–220 K and E ≥ 80–150 V/cm, the σ_d of the high-resistivity ($\sigma _{d_0 } < 10^{ - 4}$ S/cm) undoped and slightly doped (<10⁻² at % Dy) crystals increases with increasing external electric field. The observed σ_d(E) behavior is shown to be unrelated to electric-field-induced heating of charge carriers or other effects of a high electric field when carrier scattering by various point defects and phonons prevails. It is primary due to partial disorder in the crystals, the presence of drift barriers in their empty energy bands, and the influence of injection and doping levels on the dimensions of the barriers.