Hot Electron Effects and Saturation Velocities in Silicon Inversion Layers

Carrier mobility variations were measured for electrons in silicon inversion layers. Near liquid-helium temperatures and with electron densities less than about 2×1012 cm−2, the mobility increased with field and temperature. Correlation of the electron temperature with field indicates that ΔT varies with the field approximately as F3/2. Temperature dependence of the amplitude of the oscillatory magnetoconductance gave similar consistent results. At very high fields, the mobility decreased at all temperatures and electron densities. The electron drift velocity was measured for different surface orientations, substrate dopings, and ambient temperatures from 4.2° to 300°K. The drift velocity was found to saturate for fields greater than a few times 104 V/cm, depending upon the low field mobility, and was found to be lower than the reported bulk values. For (100), (111), and (110) surfaces, the limiting velocities at 300°K are (6.5±0.5) × 106, (5.5±0.5) × 106, and (4.0±0.5) × 106 cm/sec, respectively.