Generation-recombination noise in nongated and gated AlxGa1-xAs/GaAs TEGFETs in the range 1 Hz to 1 MHz

Current noise spectra were measured on low-ohmic TEGFETs (also called MODFETs or HEMTs), on nongated and gated devices. The spectra were measured with the three-point method, yielding S_I(ω), in the range 10 Hz to 1 MHz, and for temperatures of 78 to 295 K. Two to four Lorentzians were observed, which shifted to lower frequencies when the temperature decreased. The noise was clearly generation-recombination type noise, caused by conductivity fluctuations of the parallel conduction through the AlGaAs layer. Arrhenius plots gave activation energies of 240 meV, 200 meV, 130 meV, and 100 meV. These data mere also obtained from the plateau values. A new, general description for trapping noise was developed, which extends the previous results by Copeland [1971] and by Van Rheenen [1987]