  A method to incorporate polarization charges at heterojunctions in compact
models for transistors is presented. By including the polarization sheet charge
as a Dirac delta function, the Poisson equation is solved to yield a closed
equation for the surface potential. A compact model for transistors based on
the surface potential incorporating polarization charges describes the on-state
as well as the off-state regimes of device operation. The new method of
incorporating polarization charges in compact models helps make a direct
connection to the material properties of the transistor. The current-voltage
(I-V) curves generated by this model are in good agreement with the
experimental data for GaN HEMTs.
