Monte Carlo Simulation of Non-Local Transport Effects in Strained Si on Relaxed Si1 – xGex Heterostructures

F Gámiz,J A López-Villanueva,J B Roldán

doi:10.1155/1998/48528

Abstract

Electron transport properties of strained-Si on relaxed Si1 – xGex channel MOSFETs have been studied using a Monte Carlo simulator. The steady- and non-steady-state high-longitudinal field transport regimes have been described in detail. Electronvelocity- overshoot effects are studied in deep-submicron strained-Si MOSFETs, where they show an improvement over the performance of their normal silicon counterparts. The impact of the Si layer strain on the performance enhancement are described in depth in terms of microscopic magnitudes.

Highlights

Both theoretical and experimental works have shown important electron mobility enhancement when silicon is grown pseudomorphically on relaxed Sil_xGex at different temperatures
The strain causes the six-fold degenerate valleys of the silicon conduction band minimum to split into two groups: two lowered valleys with the longitudinal effective mass axis perpendicular to the interface, and four raised valleys with the longitudinal mass axis parallel to the interface
In the lowered valleys, which are more populated in the strained case, electrons show a smaller conduction effective mass in transport parallel to the interface

Summary

INTRODUCTION

Both theoretical and experimental works have shown important electron mobility enhancement when silicon is grown pseudomorphically on relaxed Sil_xGex at different temperatures. The strain causes the six-fold degenerate valleys of the silicon conduction band minimum to split into two groups: two lowered valleys with the longitudinal effective mass axis perpendicular to the interface, and four raised valleys with the longitudinal mass axis parallel to the interface. This splitting reduces the intervalley phonon scattering rate compared with that of unstrained silicon. The lower intervalley-scattering rates make the energy relaxation times higher, originating important electron velocity overshoot. These advantages can be used to improve MOSFETs parameters, taking advantage both of the higher carrier mobility and the higher electron velocity overshoot, greatly improving short channel MOSFET transconductance

MONTE CARLO SIMULATOR

RESULTS

CONCLUSIONS