Analysis of Electron Mobility in Inversion-Mode $\hbox {Al}_{2}\hbox {O}_{3}/\hbox {In}_{x}\hbox {Ga}_{1 - x}\hbox {As}$ MOSFETs

The electron mobility in Al₂O₃/InxGa_1-xAs (x = 0.53, 0.65, or 0.75) metal-oxide-semiconductor field-effect transistors was analyzed for scattering by oxide charge, as well as interface charge and roughness, and compared with measured transfer characteristics from depletion to inversion. The analysis showed that, under strong inversion, the electron mobility was mainly limited by interface roughness. The extracted interface roughness from the measured data was two to seven times that of the interface between a high-k dielectric and Si, assuming the correlation lengths were comparable. Therefore, to fully benefit from the high bulk mobility of InGaAs, its interface roughness with the gate oxide needs to be further improved.