Proposal and Experimental Demonstration of Ultrathin-Body (111) InAs-On-Insulator nMOSFETs With L Valley Conduction

Abstract

Ultrathin-body (UTB) (111) InAs-On-Insulator (InAs-OI) n-channel metal–oxide–semiconductor field-effect transistors (nMOSFETs) are proposed as a new technology booster using the L valley conduction in III–V channels. The performance of the conventional UTB III–V nMOSFETs is limited by the essential band features of the $\Gamma $ valley conduction such as the low density of states, resulting in low inversion capacitance, and the light effective mass ${m}_{z}$ along the confinement direction, resulting in strong thickness fluctuation scattering. The strong confinement of electrons by a combination of (111) surface orientation and UTB InAs-OI structures is expected to transfer the electrons into the L valley with much heavier ${m}_{z}$ than in the $\Gamma $ valley, leading to higher semiconductor capacitance and suppression of thickness fluctuation scattering. We also experimentally demonstrate the UTB (111) InAs-OI nMOSFETs operation with thinning the InAs channels down to 3 nm, realized by the smart-cut and digital etching process. Channel thickness scaling improves both the OFF- and ON-currents by expansion of the effective bandgap. It is shown that the measured mobility increases with decreasing InAs-OI thickness from 4.8 to 4.4 nm, which is attributable to the increase in the electron occupancy in the L valley.