The metalliclike conductivity of a two-dimensional hole system

We report on a zero magnetic field transport study of a two-dimensional, variable-density, hole system in GaAs. As the density is varied we observe, for the first time in GaAs-based materials, a crossover from an insulating behavior at low density, to a metalliclike behavior at high density, where the metallic behavior is characterized by a large drop in the resistivity as the temperature is lowered. These results are in agreement with recent experiments on Si-based two-dimensional systems. We show that, in the metallic region, the resistivity is dominated by an exponential temperature dependence with a characteristic temperature which is proportional to the hole density. © 1998 American Physical Society.