Computation of subthreshold slope in submicron HEMT with parasitic effects

Abstract

The subthreshold slope of a submicron high-electron-mobility transistor (HEMT) is analytically computed as a function of vertical electric field for various parasitic effects and structural parameters. The simultaneous solution of Poisson’s equation and the carrier density equation provides drain current from which subthreshold slope is calculated subject to appropriate boundary conditions. Simulation is carried out at optimised channel length and applied bias for which maximum transconductance and higher differential conductance are already reported. Results show that for a particular range of gate-to-source bias, V GS, simulated findings match very closely to the ideal value of 60 mV/decade. The role of an aluminium nitride (AlN) buffer layer in tailoring the subthreshold slope magnitude is critical and the effect of submicron channel length, which is otherwise absent in conventional HEMTs, is explored. A combination of both the electric fields in realistic situations is investigated, the findings of which will play a key role in device application for wireless communication systems.