Diameter Dependence of Spin Relaxation in Silicon, Silicon-Germanium (Si_(0.7)Ge_(0.3)) and Strained Silicon-Germanium (Si_(0.8)Ge_(0.2)/Si_(0.5)Ge_(0.5)) Nanowires

摘要

In this article, we used multi-subbands semi-classical Monte-Carlo simulation to investigate spin polarized transport in silicon, silicon-germanium (Si_(0.7)Ge_(0.3)) and strained-silicon-germanium (Si_(0.8)Ge_(0.2)/Si_(0.5)Ge_(0.5)) nanowires. Charge transport in devices has been extensively studied using Monte-Carlo simulation method and in recent past spin transport in devices has been investigated using Monte-Carlo method with the help of spin density matrix calculations. Spin dephasing in silicon, silicon-germanium (Si_(0.7)Ge_(0.3)) and strained-silicon-germanium (Si_(0.8)Ge_(0.2)/Si_(0.5)Ge_(0.5)) nanowires occur due to Elliott-Yafet relaxation mechanism and D'yakonov-Perel relaxation mechanism. In this work, we studied spin polarized transport along the length of the silicon, silicon-germanium (Si_(0.7)Ge_(0.3)) and strained-silicon-germanium (Si_(0.8)Ge_(0.2)/Si_(0.5)Ge_(0.5)) nanowires. The components of ensemble averaged spin vector are also calculated along the length for silicon, silicon-germanium (Si_(0.7)Ge_(0.3)) and strained-silicon-germanium (Si_(0.8)Ge_(0.2)/Si_(0.5)Ge_(0.5)) nanowires. Finally, the effect of variation of diameter on spin dephasing length in silicon, silicon-germanium (Si_(0.7)Ge_(0.3)) and strained-silicon-germanium (Si_(0.8)Ge_(0.2)/Si_(0.5)Ge_(0.5)) nanowires has been studied and it is found that as the diameter increases spin dephasing length also increases for very thin nanowires and beyond a certain diameter spin dephasing length becomes saturated. The dominant region behind this is the surface roughness scattering, which gradually reduces for larger diameter of nanowires and is a major contributor in the total scattering rate.