Electrical transport studies on a disordered two-dimensional electron system

In any two-dimensional (2D) system, such as an active region of many semi-conductor transistors, it had been expected in the absence of a magnetic field any amount of disorder would prevent conduction at T = 0. Experiments on a disordered 2D electron system in silicon have shown an unexpected metal insulator transition (MIT) at a critical density n_c( B = 0). This MIT was investigated by measuring the conductivity as a function of: temperature (T), electric fields ( E), and parallel magnetic fields (B).; Scaling of the non-linear response near the critical region as a function of temperature, electric fields, and parallel magnetic fields, indicate the occurrence of a quantum phase transition.; In a parallel magnetic field, the critical density was observed to increase as n_c(B) − n _c(0) ∝ B0.9 at low fields (B < 2 T). Increasing to higher fields, the data suggests a saturation of n_c(B) which is complemented by the survival of the metallic phase at parallel magnetic fields up to 18 T. It was found the metallic phase in the range of 0 ≤ B ≤ 18 T can be expressed as σ(n_s, B, T) = σ( n_s, B, T = 0) + C(n_c( B)TΛ(B ).