Strongly Anisotropic Hopping Conduction in (Ga, Mn)As/GaAs

We report magnetotransport of (Ga, Mn)As below 1 K in the reentrant insulating phase. The external magnetic field drove the samples from the strongly insulating regime to the variable range hopping one. Below 1 K, the resistivity was strongly anisotropic (by about two orders of magnitude). The conduction along the highly resistive direction ([110]) was well described by variable range hopping in the soft Coulomb gap regime while that along the lower resistive direction ([110]) seemed to undergo an insulator-to-metal transition by the external magnetic field. The result may be a key to solve the problem of reentrant metal-to-insulator transition in (Ga, Mn)As with increasing Mn content.