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

• Published in: Advances in condensed matter physics 2015-01, Vol.2015 (2015), p.1-8
• Main Authors: Bouhassoune, Mohammed, Schindlmayr, Arno
• Format: Article
• Language: English
• ISSN: 1687-8108; 1687-8124; 1687-8124
• DOI: 10.1155/2015/453125

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.