Investigation and modeling of impact ionization with regard to the RF- and noise behaviour of HFET

A new small-signal and noise equivalent circuit for Heterostructure Field-Effect Transistors (HFET), including the influence of impact ionization and gate-leakage current on the electronic properties, is presented. The capability of the new model is demonstrated by bias-dependent investigations of the RF- and noise behaviour of InAlAs-InGaAs-InP HFET.