ELECTRON LOCALIZATION AND NOISE IN SILICON-CARBIDE INVERSION-LAYERS

In silicon carbide inversion layers, a high interface disorder results in the existence of numerous localized states and in a thermally acti vated transport, even at room temperature. The minimum value of the co nductivity intercept sigma(int) is close to 0.1 <e(2)/(h)over bar>, an d the activation energy E(A) has a strong dependence on gate voltage. Low-frequency noise measurements indicate that the noise power spectra l density of the conductivity could be due to mobility fluctuations ra ther than fluctuations in the number of carriers via trapping-detrappi ng into the insulator. The system follows the Hooge relation, and the number of electrons which is relevant for application of the formula i s exactly equal to the number of carriers excited above the mobility e dge. Also, the noise measurements confirm that the change in sigma(int ) with electron concentration N-S results mainly from a change in the Fermi level with temperature, and not from a change in the pre-exponen tial factor of the conductivity with N-S.