Physical investigation of gate capacitance in In0.53Ga0.47As/In0.52Al0.48As quantum-well metal-oxide-semiconductor field-effect-transistors

In this paper, we aim to decompose gate capacitance components in InGaAs/InAlAs quantum-well (QW) metal-oxide-semiconductor field-effect-transistors (MOSFETs), in an effort to physically investigate their gate capacitance (Cg). First, we verified their validity with 1-D simulation and experimental Cg data in various types of InGaAs/InAlAs QW MOSFETs with different channel thickness (tch). Both quantum capacitance (CQ) and centroid capacitance (Ccent) were highly relevant to total gate capacitance (Cg) of the InGaAs/InAlAs QW MOSFETs. Second, the total Cg did not saturate at a strong inversion regime. This is a consequence of the second subband inversion layer capacitance (Cinv_2) and, more importantly, its increase with VG. Lastly, we studied the role of channel thickness (tch) scaling, which helps to increase the total gate capacitance by enhancing both CQ and Ccent.