Noise voltage and instability in GaAs devices

Abstract
Low-frequency current noise that has a f−3/2 power law noise spectrum is observed in GaAs field-effect devices. We show that this is due to modulation by a thermally activated and bias-independent voltage noise in the gate. We identify this noise with generation recombination associated with the semi-insulating substrate supporting these devices. Lowering the activation energy of these traps by the drain bias causes instability in this noise process, leading to low-frequency oscillations that have previously been identified with high field domains in the substrate material.