Modelling the threshold voltage of p-channel enhancement-mode GaN heterostructure field-effect transistors

p-Channel gallium nitride (GaN) metal-oxide-semiconductor heterostructure field-effect transistors utilising a polarisation induced two-dimensional hole gas operate inherently in depletion mode. The condition for their conversion to enhancement-mode operation is examined via analytical expressions for the threshold voltage and verified via technology computer-aided design (TCAD) simulations. Between the two heterostructures: (i) conventional GaN/aluminium GaN (AlGaN)/GaN and (ii) alternate AlGaN/GaN/AlGaN/GaN examined in this work, the authors demonstrate at higher threshold voltage (> vertical bar-2 vertical bar V), the alternate heterostructure can potentially achieve a higher on-current by a factor of 2 of (similar to 30 mA/mm), without degradation in the on-off-current ratio, expected ideally to be of the order of similar to 12.