Spin- and energy relaxation of hot electrons at GaAs surfaces

TL;DR

This paper reviews spin relaxation mechanisms in semiconductors, presents a kinetic equation approach for quantitative analysis, and reports that surface electrons in p-doped GaAs have longer spin relaxation times due to reduced hole density at the surface.

Contribution

It introduces a kinetic equation method for analyzing spin relaxation and explains surface-enhanced relaxation times in p-doped GaAs.

Findings

Surface electrons in p-doped GaAs have longer spin relaxation times than bulk.

Reduced hole density at the surface explains longer relaxation times.

Kinetic equations provide quantitative results beyond traditional approximations.

Abstract

The mechanisms for spin relaxation in semiconductors are reviewed, and the mechanism prevalent in p-doped semiconductors, namely spin relaxation due to the electron-hole exchange interaction, is presented in some depth. It is shown that the solution of Boltzmann-type kinetic equations allows one to obtain quantitative results for spin relaxation in semiconductors that go beyond the original Bir-Aronov-Pikus relaxation-rate approximation. Experimental results using surface sensitive two-photon photoemission techniques show that the spin relaxation-time of electrons in p-doped GaAs at a semiconductor/metal surface is several times longer than the corresponding bulk spin relaxation-times. A theoretical explanation of these results in terms of the reduced density of holes in the band-bending region at the surface is presented.