Effect of Al2O3/InGaAs Interface on Channel Mobility

In this paper, we discuss the effect of Al2O3/InGaAs interface on In0.53Ga0.47As quantum-well MOSFET channel mobility. We fabricated Al2O3 (gate dielectric)/In0.53Ga0.47As-In0.52Al0.48As (barrier)/In0.53Ga0.47As (channel) structures to study effects of gate dielectric thickness and barrier thickness on channel carrier mobility. Hall measurements were used to examine the mobility. The mobility was invariant with varying gate dielectric thickness, suggesting that charges trapped within the Al2O3 do not affect mobility significantly. The mobility varies with varying barrier thickness suggesting that Al2O3/In0.53Ga0.47As interfacial charges affect mobility. In our case, when the barrier thickness <5 nm, the mobility is dominated by coulomb scattering from interfacial charges; when the barrier thickness >5 nm, the mobility is dominated by internal phonon scattering. A model was developed to fit the experimental data and this model could be used to sample MOSFET designs that are limited by phonon scattering and gate dielectric/barrier layer interfacial charge density.