An Analytical Charge based Drain Current Model for Insulated Gate Undoped AlGaN/GaN Heterostructure

An analytical investigation of the electrical characteristics of undoped GaN/AlxGa1-xN (x is the mole fraction of Al in AlGaN) insulated gate heterostructure field effect transistor (HFET) is carried out. A self-consistent solution of Schrodinger equation and Poisson’s equation is used to formulate the relations between the two-dimensional electron gas (2 DEG) concentration, the Fermi level in GaN, and the applied gate to source bias. Also both the spontaneous and piezoelectric polarization at the AlGaN/GaN interface and the parasitic source/drain resistances has been incorporated in the analysis. Based on these developments, a model for the threshold voltage and the drain current is developed. In computation of the same, field dependent mobility and velocity saturation of typical GaN/AlGaN heterostructure are taken into account. Without any intentional doping, 2-DEG having densities in the orders of 1016/m2 and high channel current densities are found to exist. The effects of varying the dielectrics and their thicknesses as well as the aluminum mole fraction on the device characteristics are presented.