A novel analytic model for HEMT is developed. In this model

the empirical formula suggested by Giblin et al. is used to approach the behavior of electron drift velocity vs. electric field. The diffurion component of current and the effect of the parasitic resistance of the undoped GaAs buffer layer are properly involved. The calculated current-voltage characteristics agree well with experimental data. Using this model

the parameters of HEMT such as channel conductance

transconductance

gate capacitance

and cut-off frequency are derived.