The channel mobility in SiO₂/GaN hybrid metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) has been studied. The formalism used for the inversion mobility in MOSFETs has been adapted to the case of GaN MOS-HEMTs, which operate in accumulation condition. Using the values of interface trapped charges (Qtrap= 1.35 x 10¹² cm⁻ ²) and surface roughness (RMS= 0.15 nm) determined by capacitance-voltage measurements and nanoscale morphological analyses allowed to derive ...