New Light on the Scattering Mechanisms in Si Inversion Layers by Weak Localization Experiments

Abstract

The quasi two-dimensional resistivity and magnetoresistance has been measured on Si(100) MOSFET electron inversion layer as a function of carrier density, temperature and magnetic field. The magnetoresistance is interpreted by the weak localization theory, and we determine the phase relaxation time. The phase relaxation rate has three components, of which two can be identified as the electron-electron scattering rate and the so-called Nyquist (or impurity mediated electron-electron) scattering rate. A third contribution becomes important at low carrier densities and suggests itself as being related to the screened impurity relaxation rate, which however is normally considered to be elastic and therefore should not contribute to the phase relaxation. The screened impurity relaxation rate and the Nyquist scattering rate are the dominating contributions to the temperature dependent mobility of our samples. The screened impurity relaxation rate is compared to recent calculations by Gold and Dolgopolov. At magnetic fields intermediate between the weak-localization-regime and the Landau-level-dominated-regime the weak localization magneto-resistance has been measured and compared to current theories.