Monte Carlo simulation of electron transport in simple orthorhombically strained silicon

We report on the electron transport properties of simple orthorhombically strained silicon studied by density-functional theory and Monte Carlo simulation. The six degenerate valleys near X points in bulk silicon break into three pairs with different energy minima due to the orthorhombic strain. The degeneracy lifting causes electron redistribution among these valleys at low and intermediate electric fields. Thus the drift velocity is enhanced under an electric field transverse to the long axis of the lowest valleys. Orthorhombically strained layers should be of interest in vertical SiGe-based heterostructure n-channel-metal-oxide-semiconductor field effect transistors. The simple orthorhombically strained Si grown on a Si_0.6Ge_0.4 sidewall has a low-field mobility almost twice that of bulk Si and an electron saturation velocity approximately 20% higher.