Paper detail

Spin relaxation in a zinc-blende (110) symmetric quantum well with delta-doping

The spin relaxation of a two-dimensional electron system (2DES) formed in a symmetric quantum well is studied theoretically when the quantum well is parallel to the (110) plane of the zinc-blende structure, the spin polarization is perpendicular to the well, and electrons occupy only the ground subband. The spin relaxation rate is calculated as a function of the distribution of donor impurities which are placed in the well layer. Considered processes of the spin relaxation are (1) intrasubband process by impurity-potential-induced spin-orbit interaction (SOI), which is the Elliott-Yafet mechanism in the 2DES, and (2) virtual intersubband processes consisting of a spin flip by (2a) well-potential-induced SOI or (2b) the Dresselhaus SOI, and a scattering from an impurity. It is shown that all of the above processes disappear, when all impurities are located on the center plane of the well. Even if impurities are distributed over three (110) atomic layers, the spin relaxation rate is two orders of magnitude lower than that for the uniform distribution over the well width of 7.5\ nm. In GaAs/AlGaAs type-I quantum wells the processes (1) and (2a) interfere constructively, being dominant over (2b) for the well width of $\sim$10\ nm, while in some type-II quantum wells they can interfere destructively.