Role of free holes in nBTI degradation in GaN-on-Si MOS-channel HEMTs

To understand the peculiar kinetic of the negative Bias Temperature Instabilities (nBTI) in GaN-on-Si MOS-channel HEMTs (MOSc-HEMTs), temperature (T), gate bias (V
G,stress
) and modification of the epitaxial structure are used to determine if free holes are responsible for long-term threshold voltage (Vth) shift. Furthermore, UV assisted nBTI measurements were carried out to stimulate free holes generation in the epitaxy structure near the gate. TCAD simulations validate the assumption that nBTI is a multifactorial degradation mixing free holes capture in the Al
2
O
3
gate oxide and C
N
deep acceptor charge state modification in the buried GaN:C layer.