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

Abstract

Based on Monte Carlo simulation, we report the study of the inversion layer mobility in n-channel strained Si/ Si 1-x Ge x MOS structures. The influence of the strain in the Si layer and of the doping level is studied. Universal mobility curves µ 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/ Si 0.70 Ge 0.30 , 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.

Influence of Ballistic Effects in Ultra-Small MOSFETs

“…The on-current is defined as the current at [3]. On one hand, we have observed (not shown here) a mobility enhancement with strain when compared to the case of bulk Si, with a saturation phenomenon when x reaches 0.15 [3].…”

“…We consider scattering mechanisms related to phonons, ionized impurities, SiO 2 /Si surface roughness and alloy in SiGe, within an analytical band structure (see Ref. [2,3] for more details). Quantization effects are not taken account.…”

Electron transport properties in high-purity Ge down to cryogenic temperatures

“…Ionized impurity scattering is treated via the screened Coulomb potential using a momentum-dependent screening length L defined by Takimoto 12 : all details of the model may be found in Ref. [11]. Results are presented here for a net density of ionized impurities of 10 10 cm -3 , which is the typical order of magnitude of the residual density of impurities in high-purity Ge.…”

Current transport models for nanoscale semiconductor devices

“…Therefore, the full power of three-dimensional full-band Monte Carlo methods which include accurate band-structure and scattering processes to obtain transport characteristics in inversion layers and SOI structures can be applied [8,121]. Recently, mobility of stressed Si/SiGe inversion layers was investigated [122][123][124]. Interestingly, due to a concentration decrease at the interface, the surface roughness scattering is underestimated, which requires special corrections [125].…”