Metallic Behavior in Dilute Two-Dimensional Hole Systems

We have studied the metallic behavior in low-density two-dimensional $p$-GaAs systems, close to the apparent metal-insulator transition. Two observations are made concerning the origins of the metallic-like behavior. Within a given sample the strength of the metallic behavior is almost independent of the asymmetry of the confining potential, and is predominantly determined by the low-temperature resistivity (i.e., by $k_{F}l$). In all our samples we find that at low densities, close to the transition from insulating to metallic behavior, the fractional decrease in conductivity with increasing temperature scales as ${T/T}_F$.