NONLINEAR RESISTIVITY AT THE METAL-INSULATOR-TRANSITION IN A 2-DIMENSIONAL ELECTRON-GAS

We have experimentally investigated the nonlinear resistivities occurr ing close to the metal-insulator transition in high mobility Si MOSFET 's. The numerical values for the critical electron density, similar to 8 X 10(14) m(-2), and the critical resistance, similar to 3 h/e(2), i n a variety of samples of different sizes from 2 X 8 mu m to 50X120 mu m, agree with previously published data. Electric-field- and temperat ure-dependent scaling are applied. From the scaling, we derive z = 1.1 4+/-0.18 for the dynamical scaling parameter and v = 1.87+/-0.24 for t he correlation length exponent, but question experimentally the range of validity of the scaling theory. We relate the nonlinear resistiviti es observed for interacting electrons to the observed high-temperature resistivity due to predominantly noninteracting electrons.