Mobility Degradation Effect to Hooge's Constant in Recessed-Gate ${\rm Al}_{2}{\rm O}_{3}/{\rm AlGaN}/{\rm GaN}$ MIS Power Transistors

We investigated the low-frequency noise (LFN) characteristics of recessed-gate Al
₂
O
₃
/AlGaN/GaN MIS power transistors. Compared with normally ON devices, the gate-recess processes are only added in normally OFF devices. The extracted threshold voltage (V
_th
) values of the normally ON and normally OFF devices are -7 and 4 V, respectively. However, the normally OFF devices additionally suffer from mobility degradation. Furthermore, the Hooge's constant (α
_H
) of the normally OFF devices is ~15 times higher than that of the normally ON devices. From the LFN measurement results, the main cause for this significant difference is the mobility fluctuation due to impurity scattering in the recessed-gate devices.