Strained Si/SiGe Heterostructures at Low Temperatures. A Monte Carlo Study

Abstract
Monte Carlo simulations are used to study the transport properties of electrons in strained silicon inversion layers in Si/SiGe MOSFETs at low temperature. The strain produces an enhancement of electron mobility due to the reduction of intervalley scattering and a lower effective conduction mass as a consequence of the valley splitting. In this work, mobility curves for different Ge concentrations are obtained by Monte Carlo simulation at both low and room temperatures. It has been observed that at room temperature mobility enhancement saturates at a Ge concentration close to x=0.3, while the mole fraction of Ge at which the electron mobility curves saturate is much lower at low temperature. In addition, the relative enhancement at low temperatures is much less than at room temperature. Finally, mobility curves show a tendency to coincide at high transverse electric fields, regardless of the Ge concentration, as a consequence of the greater concentration of electrons in the ground subband.