Electron and hole mobilities in orthorhombically strained silicon

Carrier transport in orthorhombically strained Si is theoretically analyzed. Calculations are based on a 16 x 16 Hamiltonian matrix constructed from the linear combination of atomic orbital approximation with spin-orbit interaction and strain effect taken into account. In the case of electrons, there is a little difference between orthorhombic and biaxial strains. The phononlimited hole mobility is about 1200cm(2)/(Vs) under orthorhombic strain at a Ge content of 30%. A strong hole mobility enhancement relative to unstrained bulk Si is found, ranging from a factor of two at a Ge content of 20% up to a factor of about three at a Ge content of 40%. The enhanced material properties make orthorhombically strained Si attractive for novel device applications, although the improvements are not as large as for biaxial tensile strain.