Investigation of electron mobility in surface-channel Al2O ₃/In_0.53Ga_0.47As MOSFETs

We report on the mechanisms limiting the electron mobility in surface-channel Al2O3/InGaAs MOSFETs. The electron mobility was obtained using pulsed Id- Vg and split C-V measurements. The energy profile of the density of interface states along with the equivalent-surface density of fixed positive oxide charge were obtained from the modeling of the gate-to-channel capacitance versus gate voltage (Cgc- Vg) characteristic. The experimental Cgc- Vg characteristic was modeled using a self-consistent Poisson-Schrödinger solver, while the electron mobility was calculated using the Kubo-Greenwood formula with nonparabolic corrections. Even when taking into account the impact of fixed oxide charges, Al2O3/In0.53- Ga0.47As interface states within the In0.53Ga0.47As energy gap and aligned with the conduction band and the impact of remote phonon scattering, the mobility calculations revealed that the Al2O3/In0.53Ga0.47As surface roughness was the dominant mechanism limiting the electron mobility at high inversion charge density. The values of surface roughness predicted from the combined modeling and experimental results were confirmed by atomic force microscopy measurements and the process step responsible for the increased InGaAs surface roughness was identified.