Electron Momentum and Spin Relaxation in Silicon Films: A Rigorous k p-based Approach

Growing technological challenges and soaring costs are gradually bringing the MOSFET scaling to an end. This intensifies the search of alternative technologies and computational principles. The electron spin attracts attention as a possible candidate to be used in future electron devices for complimenting or even replacing the charge degree of freedom employed in MOSFETs. The spin state is characterized by the two spin projections on a given axis and it thus has a potential in digital information processing. In addition, only a small amount of energy is needed to flip the spin orientation. Silicon is an ideal material for spintronic applications due to the long spin lifetime in the bulk. The spin lifetime is determined by the spin-flip scattering between the valleys located on different crystallographic axes [1]. This mechanism is suppressed in thin films; however, large spin relaxation in gated silicon structures was observed [2]. Understanding the spin relaxation mechanisms and ways to boost the spin lifetime in confined electron systems is urgently needed. We investigate the spin relaxation in (001) silicon structures by taking into account surface roughness and electron-phonon scattering. The surface roughness scattering matrix elements are proportional to the product of the corresponding subband wave functions derivatives at each interface