Investigation of electron mobility in surface-channel Al_2O_3/In_(0.53)Ga_(0.47)As MOSFETs

摘要

We report on the mechanisms limiting the electron mobility in surface-channel Al_2O_3/lnGaAs MOSFETs. The electron mobility was obtained using pulsed I_d - V_g 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 (C_(gc) - V_g) characteristic. The experimental C_(gc) - V_g characteristic was modeled using a self-consistent Poisson-Schroedinger 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, Al_2O_3/In_(0.53)-Ga_(0.47)As interface states within the In_(0.53)Ga_(0.47)As energy gap and aligned with the conduction band and the impact of remote phonon scattering, the mobility calculations revealed that the Al_2O_3/In_(0.53)Ga_(0.47)As 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.