Current—voltage characteristics of an AlGaAs/GaAs heterostructure FET for high gate voltages

Drain-to-source current for high gate voltages in AlGaAs/GaAs heterostructure FET´s (HFET´s) is found to depend on the electron saturation velocity in the AlGaAs layer. A simple model, which takes into account the current through the undepleted channel in the AlGaAs layer as a function of the electron saturation velocity in AlGaAs, is proposed for describing I-V characteristics of HFET´s for high gate voltages. Using the model, effective electron saturation velocity in AlxGa1-xAs for different Al content levels has been obtained from the analysis of the present experimental results; 7 × 10⁶cm/s for x = 0.24 and 3 × 10⁶cm/s for x = 0.3 at a 4 × 10¹⁷cm^-3doping concentration.