Electron spin relaxation via tunneling-activated Dresselhaus spin–orbit fields in semiconductor superlattices

Abstract

Controlling electron spin relaxation is a critical technology in semiconductor spintronics. In (110)-oriented GaAs/AlGaAs quantum wells (QWs), the D'yakonov–Perel (DP) mechanism—a relevant relaxation mechanism of electron spins perpendicular to the (001) QWs at room temperature—is substantially suppressed. However, in (110) superlattices (SLs), spin relaxation time τs has been observed to be dependent on the tunnel barrier thickness. Here, we developed a model in (110) SLs where the non-zero momentum of electrons along the stacked direction generates an in-plane component of the effective magnetic field Beff, which is a driving force for DP spin relaxation. We investigate τs in GaAs/AlGaAs (110) SLs, where the structural parameters are systematically varied. Monte Carlo simulation considering spin precession around Beff in modified band structures in SLs quantitatively reproduced the experimental observations that τs depends on both the tunnel-coupling strength and the number of periods. The results demonstrate that our simulation employing pseudo-potential approximation provides useful methods for studying spin dynamics in band-engineered quantum structures and designing spintronics devices.