Author : Lan Qing
Publisher :
ISBN 13 :
Total Pages : 141 pages
Book Rating : 4.:/5 (96 download)
Book Synopsis Spin Transport in Semiconductors Manipulated by Extrinsic Factors by : Lan Qing
Download or read book Spin Transport in Semiconductors Manipulated by Extrinsic Factors written by Lan Qing and published by . This book was released on 2015 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Spin transport in semiconductors is of fundamental research interest not only for addressing basic solid state physics aspects, but also for the already demonstrated potential it has in electronic and storage technologies. The centerpiece of spin-dependent transport focuses on the spin relaxation. So far, spin lifetimes deduced from many spin transport measurements indicate certain discrepancies with the theoretical values developed from intrinsic electron-phonon interactions in equilibrium. Detailed investigation for each of the experiments is needed in order to fill the gap, and here we show how these spin transports in semiconductors can be manipulated by extrinsic factors, such as external field, doping-induced exchange, and device structure. The comprehensive consideration of all these influences results in a consistent agreement between theory and experiment, as well as a transparent physical picture. Electric fields can drive electrons away from thermal equilibrium and substantially enhance the dominant spin relaxation mechanism in silicon and germanium. Empirical results from spin transport devices with ballistic injection confirms our theory for such strong spin depolarization. It enables the optimization of spintronics devices, as we can choose the electric field that optimizes the tradeoff between fast transport across the device and signal loss due to spin depolarization. The scenario is more promising when applying strainches Meanwhile, at low temperatures conduction electrons accelerated by electric fields can also excite the localized electrons frozen at the doped impurities via inelastic scattering. Promotion into highly spin-mixed localized states leads to spin depolarization that couples strongly to the conduction electrons by exchange interaction. This novel spin relaxation mechanism is a key ingredient when one tries to model the anomalous behaviors observed at low temperatures. The exchange between conduction and localized electrons can play an important role as well in electrical Hanle effect measurement. A unique Lorentzian-shaped signal is discovered in both theory and experiment. Its shape does not directly relate to spin relaxation as commonly believed. This effect together with the briefly discussed impurity-assisted tunneling magnetoresistance elucidates the reliability of the spin lifetime extracted from a three-terminal device geometry. The spin dynamics with extrinsic factors developed in this thesis possesses broad applications. We show two practical cases in optical orientation that exhibit an outlook beyond spin transport. The examined evolutions of hot electrons and the corresponding spin properties reveal the underlying physics of crystal symmetry and band structures. The method can be further utilized to complete the picture of spin relaxation in semiconductors, and to analyze the extrinsic spin Hall effect"--Pages viii-ix.
