GENERATION-RECOMBINATION NOISE IN ALXGA1-XAS - TEMPERATURE-DEPENDENCE

Voltage noise in Si-doped AlxGa1-xAs epilayers was investigated in the frequency range of 1 Hz to 100 kHz and in the temperature range of 80-340 K. In addition, the Hall mobility and the resistivity were measured as a function of temperature in the same temperature range. The noise spectra consisted of a frequency- and current-independent part and a frequency- and current-dependent part. The frequency-dependent part consisted of one or two Lorentzians and depended quadratically on the applied current indicating that it was caused by resistivity fluctuations. These Lorentzians were therefore interpreted in terms of generation-recombination processes. Using a model involving two types of localised centres in the forbidden gap and including the effect of the secondary valleys it was possible to explain both the Hall effect and the characteristic times and magnitudes of the various generation- recombination components in the spectra as functions of the temperature with the help of computer calculations. From these calculations the energy positions in the forbidden gap, the electron capture cross sections and information about the concentrations of the two centres could be obtained.