Percolation Induced Metal-Insulator Transition in 2D Si/SiGe Quantum Wells

Since the first observations metallic behavior in Si-MOSFETs (Silicon-Metal Oxide Semiconductor Field Effect Transistor), the nature of the metal insulator transition in two-dimensional (2D) systems has remained a controversial issue and the temperature coefficient of conductivity (TCC = d sigma/dT) can give a false conception on the critical density of the transition from a metallic side to an insulating side (or vice versa). In this paper the density (p) dependence of the conductivity of 2D hole gas confined in gated Si/SiGe/Si quantum wells was analyzed in the metallic side (p >= 1.610(11) cm(-2)) at very low temperature. Our investigation reveals a density inhomogeneity driven percolation-type transition and gives values of the critical densities lower than those indicated by the sign of the slope d sigma/dT.