Variable Range Hopping Conduction in Al_0.3Ga_0.7As:Si

Abstract

We report variable range hopping conduction (VRHC) in the insulating phase near the metal-insulator transition in Al_0.3Ga_0.7As:Si. In the VRHC region, the temperature dependence of the resistivity obeys Efros and Shklovskii’s T^1⁄2 law rather than Mott’s T^1⁄4 law. This means the Coulomb repulsion effect is important to the transport in this system. These results and those of dielectric constant measurements reported previously are explained by Efros and Shklovskii’s theory. On the other hand, the magnetoresistance in VRHC is negative; no clear theoretical explanation has been found for this.