Model for electron mobility as a function of carrier concentration and strain in heavily doped strained silicon

Abstract

Strain engineering plays a pivotal role in modern devices due to the advantages it offers in enhancing carrier mobility, μ. In addition to strain, ε, carrier concentration, N, also determines mobility and an understanding of the functional dependence μ(N,ε) at various levels of strain is vital. Although well established for low and moderate doping, currently little is known about μ(N) for high carrier concentrations (>1019 cm−3) in strained Si. We present experimental data to fill this void, allowing an extension of the current model for μ(N) [Masetti et al., IEEE Trans. Electron DevicesIETDAI0018-9383 30, 764 (1983)] to account for strain. We also consider the influence of strain induced from dopant atoms. Experiments show the effects of tensile strain as a mobility enhancer are reduced but still significant at high doping concentrations. The model reproduces this effect and accounts for μ(N,ε) across the full range of doping concentrations.