Low-density finite-temperature apparent insulating phase in two-dimensional semiconductor systems

We propose that the observed low-density “insulating” phase of a two-dimensional (2D) semiconductor system, with the carrier density being just below (nnc whereas it decreases with increasing T for nnc). This low density (n<nc) finite-temperature crossover 2D effective insulating phase is characterized by ρ(T) with power-law temperature dependence in contrast to the truly insulating state (occurring at still lower densities) whose resistivity increases exponentially with decreasing temperature.