Bulk and structure inversion asymmetry in semiconductor quantum well structures

Spintronics utilizes the electron’s spin degree of freedom as information carrier. The basis of this fast growing research area is given by spin-orbit coupling (SOI), which lifts the spin degeneracy of the energy bands in low dimensional semiconductor heterostructures. The resulting spin dependent band splitting in k-space is described by the k-linear Rashba terms and the k-linear and k-cubic Dresselhaus terms in the Hamiltonian. In this work the anisotropy of the band spin splitting, which is caused by the interference of bulk and structure inversion asymmetry (BIA and SIA), is investigated experimentally in low dimensional III-V semiconductor heterostructures. Herewith, basic rules for the design of quantum well (QW) structures with a defined SIA/BIA-ratio are obtained. These goals are achieved applying a newly developed opto-electronic method, based on the analysis of the magnetogyrotropic photogalvanic effect’s (MPGE’s) anisotropy, as well as well established methods employing further photogalvanic effects. Moreover, through this work, QWs with equal strengths of k-linear Rashba and Dresselhaus spin splitting are gained. Such materials are a crucial prerequisite for future spintronic devices, since they allow the formation of a persistent spin helix (PSH). Furthermore, the study of photogalvanic effects together with magneto-transport experiments in QWs with strong SOI and numerical simulations allow estimating the influence of the k-cubic Dresselhaus terms on the PSH formation. Another aim of this work is to study the microscopic origins underlying the formation of the MPGE current. Here, we demonstrate that both spin and orbital mechanisms contribute to the linear as well as the circular MPGE in GaAs/AlGaAs QWs