NEW CONTINUOUS HETEROSTRUCTURE FIELD-EFFECT-TRANSISTOR MODEL AND UNIFIED PARAMETER EXTRACTION TECHNIQUE

A new continuous model for Heterostructure Field-Effect Transistors (HFET‘s) suitable for circuit simulation and device characterization is proposed. The model is based on the analytical solution of a two-dimensional Poisson's equation in the saturation region. The HFET saturation current and saturation voltage are experimentally determined by differentiating the output characteristics in a unified and unambiguous way. These results are used for a systematic extraction of device and process parameters such as the threshold voltage, effective electron saturation velocity and mobility, drain and source series resistances, effective gate length, and characteristic length for channel length modulation. The deduced values agree well with other independent measurements. The results of experimental studies of HFET's with nominal gate lengths of 1, 1.4, 2, and 5 μm are reported. The models and techniques presented here are successfully applied to all these devices. A large short-channel effect is observed for the 1 μm gate HFET. The gate length dependences of the device parameters uniquely determined by the method presented here reveal that the effective gate length in our self-aligned structures is approximately 0.25 μm shorter than the nominal gate length. © 1990 IEEE