In depth TCAD analysis of threshold voltage on GaN-on-Si MOS-channel fully recessed gate HEMTs

The fully recessed gate GaN-on-Si MOS-channel HEMTs (MOSc-HEMT) with Back-Barrier (BB) structure gives rise to unexpected threshold voltage (V
TH
) behaviors such as V
TH
increase with decreasing gate length (L
G
) (V
TH
roll-up) and discrepancies between V
TH
values extracted from I
D
(V
G
) (V
TH_IV
) and from C
GC
(V
G
) (V
TH_CV
) characteristics. Using TCAD simulations and experimental measurements, we demonstrate that conduction band confinement, especially at gate corners, is responsible for these peculiar V
TH
behaviors. This band confinement is strengthened by the fully recessed gate configuration coupled with the proximity of a back-barrier.