Performance Enhancement of GaAs UTB pFETs by Strain, Orientation and Body Thickness Engineering

Abhijeet Paul, Purdue University - Main Campus
Saumitra Mehrotra, Purdue University - Main Campus
Gerhard Klimeck, Purdue University - Main Campus
Mark Rodwell, University of California, Santa Barbara

Abstract

II-V semiconductors can provide a viable option for continuous scaling of future CMOS technology [1-3]. We report a significant enhancement in the ON-current (ION) of ultra-thin body (UTB) GaAs intrinsic channel p-MOSFETs using biaxial compressive strain. Our theoretical investigation shows that valence bands (VB) become hyperbolic under compressive strain in GaAs rendering effective mass approximation (EMA) invalid. The ballistic ION(~Qinv (hole density) × Vinj (injection velocity)) is governed mainly by the asymptotic group velocity (Vgrp ~ α.Vinj) of the hyperbolic VBs, These bands can be engineered using GaAs body thickness (Tch) scaling, compressive strain value and wafer orientation. Vinj is primarily controlled by strain and Tch whereas, Qinv is governed mainly by the gate electrostatics, thus providing two separate design parameters to control ION. Isotropic strain enhances Vinj which gives a maximum improvement in ION of ~23-40% for [100]/(100) and [110]/(111) pMOSFETs for 5 nm body thickness at 4% compressive biaxial strain. Scaling body thickness from 5nm to 2nm improves ION by ~2X for all the device orientations considered in this study.

Discipline(s)

Nanoscience and Nanotechnology