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

Based on Monte Carlo simulation, we report the study of the inversion layer mobility in n-channel strained-Si/Si-1-Ge-x(x) MOS structures. The influence of the strain in the Si layer and of the doping level is studied. Universal mobility curves mu(eff) as a function of the effective vertical field E-eff 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. (c) 2005 Elsevier Ltd. All rights reserved.