Channel Mobility in GaN Hybrid MOS-HEMT Using SiO2 as Gate Insulator

The channel mobility in SiO
₂
/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 (Q
_trap
= 1.35 × 10
¹²
cm
^-2
) and surface roughness (RMS = 0.15 nm) determined by capacitance-voltage-measurements and nanoscale morphological analyses allowed to derive meaningful physical parameters for the mobility model. The temperature dependence of the peak mobility-that decreases from 110 cm
²
V
^-1
s
^-1
at room temperature down to 91 cm
²
V
^-1
s
^-1
at 423 K-is mainly ruled by phonon and Coulomb scattering effects. The implications in practical devices were discussed, considering the possible improvement of the device on-resistance that can be obtained by reducing the interfaces state density at the SiO
₂
/GaN interface.