Ab Initio Study of Strain Effects on the Quasiparticle Bands and Effective Masses in Silicon

Abstract EN

Using ab initio computational methods, we study the structural and electronic properties ofstrained silicon, which has emerged as a promising technology to improve the performance of silicon-basedmetal-oxide-semiconductor field-effect transistors.

In particular, higher electron mobilitiesare observed in n-doped samples with monoclinic strain along the [110] direction, and experimentalevidence relates this to changes in the effective mass as well as the scattering rates.

To assess therelative importance of these two factors, we combine density-functional theory in the local-densityapproximation with the G W approximation for the electronic self-energy and investigate the effectof uniaxial and biaxial strains along the [110] direction on the structural and electronic properties ofSi.

Longitudinal and transverse components of the electron effective mass as a function of the strainare derived from fits to the quasiparticle band structure and a diagonalization of the full effective-masstensor.

The changes in the effective masses and the energy splitting of the conduction-bandvalleys for uniaxial and biaxial strains as well as their impact on the electron mobility are analyzed.

The self-energy corrections within G W lead to band gaps in excellent agreement with experimentalmeasurements and slightly larger effective masses than in the local-density approximation.