Strong-Inversion Model of Threshold Voltage in Modulation Doped Field Effect Transistors: The Role of Unintentional Acceptors.

摘要

A strong-inversion model, in the depletion layer approximation, of the threshold voltage for modulation doped field-effect transistors (MODFETs) has been developed. We show that for a range of unintentional acceptor doping densities from 10 to the 13th power to 10 to the 15th power per cu. cm. in typical molecular beam epitaxy (MBE) -grown structures, threshold voltages may increase by as much as 200 mV. We isolate the contributions of AlGaAs and GaAs to the threshold voltage. We have verified our model by comparing predicted threshold voltages with those measured in typical MBE-grown MODFET structures. (rh)