Spin-orbit Splittings in Si/SiGe Quantum Wells: From Ideal Si Membranes to Realistic Hterostructures
Date of this Version2009
We would like to thank N. Kharche, M. Friesen and M. Eriksson for useful conversations. This work was supported by the Spanish Ministry of Education and Science (MEC). Financial support was provided by the National Science Foundation, Grant Nos. NSF-ECS-0524253 and NSF-FRG-0805045, and by ARO and LPS, Grant No. W911NF-08-1-0482.
We present a calculation of the wavevector-dependent subband level splitting from spin-orbit coupling in Si/SiGe quantum wells. We ﬁrst use the eﬀective-mass approach, where the splittings are parameterized by separating contributions from the Rashba and Dresselhaus terms. We then determine the inversion asymmetry parameters by ﬁtting tight-binding numerical results obtained using the quantitative nanoelectronic modeling tool, NEMO-3D. We describe the relevant coeﬃcients as a function of applied electric ﬁeld and well width in our numerical simulations. Symmetry arguments can also predict the behavior, and an extensive analysis is also presented in this work. Using vast computational resources, we treat alloy disorder at atomistic scale. We obtain ﬁrst-time results for realistic Si/SiGe heterostructures. Our numerical data are in very good agreement with experimental results, both qualitatively and quantitatively. We conclude that eﬀects of alloy disorder have a crucial inﬂuence in the spin-orbit parameters.
Nanoscience and Nanotechnology