GaAs MESFET interface considerations

Various properties of GaAs MESFET´s are discussed in terms of the basic physics of interfaces and deep levels. Fermi-level pinning is shown to lead to hole injection from a positively biased metal lying in direct contact with semi-insulating GaAs. This hole injection is partially responsible for low-frequency oscillations in GaAs MESFET´s. Backgating and low-frequency oscillations are shown to be a direct consequence of the peculiar nature of the channel-substrate interface. This interface is discussed within the framework of a three-level model.