Current saturation and small-signal characteristics of GaAs field-effect transistors

Abstract

The model previously proposed by Turner and Wilson is developed in detail and compared with experiment. Deviations from Shockley's classical theory can be accounted for in terms of a single quantity Γ, which is related to Emthe peak field for GaAs. A discussion of the physical mechanism of current saturtation shows that the formation of domains within the channel is hampered in a conventional GaAs FET. Ay-parameter analysis is presented that permits calculation of transconductance and the unity current gain frequency fT. Measurements of drain current, transconductance, and fTversus gate voltage all show good agreement with values predicted by the theory. Estimates are given which show that the current saturation mechanism described will be important in the design of GaAs microwave FET's.