Low temperature characterization of effective mobility in uniaxially and biaxially strained N-MOSFETs

In this paper, a detailed investigation of the mobility in two different strained-Si technologies has been conducted. The mobility gain due to strain is nearly lost in short channel devices. The short channel loss observed in both cases is attributed to a bigger contribution of Coulomb scattering and to a larger subband splitting due to pocket implants. Finally, the mobility gain reduction with temperature lowering has been quantitatively interpreted by a simple analytical model accounting for the fourfold valley depopulation and considering different scattering rates for the two first subbands.