Effects of shear strain on the conduction band in silicon: An efficient two-band k.p theory

We present an efficient two-band k.p theory which accurately describes the six lowest conduction band valleys in silicon. By comparing the model with full band pseudo-potential calculations we demonstrate that the model captures both the nonparabolicty effects and the stress-induced band structure modification for general stress conditions. It reproduces the stress dependence of the effective masses and the nonparabolicity parameter. Analytical expressions for the valley shifts and the transversal and longitudinal effective mass modifications induced by uniaxial [110] stress are obtained and analyzed. The low-field mobility enhancement in the direction of tensile [110] stress in {001} SOI FETs with arbitrary small body thickness is due to a modification of the conductivity mass and is shown to be partly hampered by an increase in nonparabolicity at high stress value.