g-Factor Anisotropy Inversion in InGaAs 2D Nanostructures

The inversion or sign change of the electron g-factor anisotropy in thin-layer semiconductor nanostructures is investigated theoretically and gauged for InGaAs asymmetric single and double quantum wells (QWs). The g-factor anisotropy in these 2D nanostructures is given by the difference between the longitudinal and transverse components; it is a fine sensor of the confining potential and in InGaAs structures it is determined by the Rashba spin–orbit coupling. In the presence of structure inversion asymmetry (SIA) the g-factor anisotropy is expected to invert at a critical well width. This effect can be useful technologically and is here analyzed in detail with InGaAs/InP asymmetric multi-layer structures. The g-factor anisotropy in these structures is calculated in a fine grid around the inversion point, using 8-band kp Kane model based envelope function theory for the nanostructure, and perturbation theory for the calculation of the effective g factor. It is shown that the anisotropy inversion can be seen only in asymmetric structures with very thin layers, near the limit of no bound states allowed, and corresponding to the electron being pushed out of the confining region. The inversion point, or critical well width for the g-factor anisotropy inversion in Insulator/InGaAs/InP QWs is determined to be ≈4 nm. For double or coupled QWs it is found that the inversion can be observed only with very thin tunneling barriers around 1 nm wide.