Electron effective mobility in strained Si/Si1-xGex MOS devices using Monte Carlo simulation

TL;DR

This study uses Monte Carlo simulation to analyze how strain and doping affect electron mobility in Si/SiGe MOS devices, revealing mobility enhancements and degradation mechanisms relevant for device optimization.

Contribution

It provides detailed simulation-based insights into the effects of strain, doping, and channel thickness on mobility, including comparison with experimental data.

Findings

Mobility increases up to 120% in strained Si/Si0.70Ge0.30.

Mobility degradation occurs at low effective fields with decreasing channel thickness.

Simulation results align with experimental trends and highlight scattering mechanisms.

Abstract

Based on Monte Carlo simulation, we report the study of the inversion layer mobility in n-channel strained Si/ Si1-xGex MOS structures. The influence of the strain in the Si layer and of the doping level is studied. Universal mobility curves mueff as a function of the effective vertical field Eeff are obtained for various state of strain, as well as a fall-off of the mobility in weak inversion regime, which reproduces correctly the experimental trends. We also observe a mobility enhancement up to 120 % for strained Si/ Si0.70Ge0.30, in accordance with best experimental data. The effect of the strained Si channel thickness is also investigated: when decreasing the thickness, a mobility degradation is observed under low effective field only. The role of the different scattering mechanisms involved in the strained Si/ Si1-xGex MOS structures is explained. In addition, comparison with experimental results is discussed in terms of SiO2/ Si interface roughness, as well as surface roughness of the SiGe substrate on which strained Si is grown.