Effects of spin diffusion on electron spin relaxation time measured with a time-resolved microscopic photoluminescence technique

Abstract

We performed measurements at room temperature for a GaAs/AlGaAs multiple quantum well grown on GaAs(110) using a time-resolved microscopic photoluminescence (micro-PL) technique to find what effects spin diffusion had on the measured electron spin relaxation time, τs, and developed a method of estimating the spin diffusion coefficient, Ds, using the measured data and the coupled drift-diffusion equations for spin polarized electrons. The spatial nonuniformities of τs and the initial degree of electron spin polarization caused by the pump intensity distribution inside the focal spot were taken into account to explain the dependence of τs on the measured spot size, i.e., a longer τs for a smaller spot size. We estimated Ds as ∼100 cm2/s, which is similar to a value reported in the literature. We also provided a qualitative understanding on how spin diffusion lengthens τs in micro-PL measurements.