Punch-through in short-channel AlGaN/GaN HFETs

Short-channel punch-through effects are demonstrated in 0.17 μm gate length AlGaN/GaN single heterojunction field-effect transistors. These take the form of a high output conductance and the strong dependence of pinch-off voltage on drain voltage. It is shown by simulation that they can be explained by poor confinement of charge at the AlGaN/GaN interface resulting in current flow within the bulk of the GaN layer. This is caused by there being a concentration of only ∼1.5×10¹⁶ cm^-3 deep levels in the insulating GaN buffer layer. It is found that a net acceptor density of around 10¹⁷ cm^-3 is required to ensure suppression of short-channel effects.