Imaging charge and spin diffusion of minority carriers in GaAs

TL;DR

This study introduces a novel contactless optical method to measure charge and spin diffusion lengths in GaAs, revealing how surface recombination affects these properties at room temperature.

Contribution

The paper presents a new circularly polarized photoluminescence microscopy technique for measuring charge and spin diffusion lengths in GaAs.

Findings

Measured diffusion lengths agree with polarization data.

Surface recombination sharply reduces charge and spin diffusion lengths.

Outward diffusion increases polarization at the excitation spot.

Abstract

Room temperature electronic diffusion is studied in 3 mum thick epitaxial p+ GaAs lift-off films using a novel circularly polarized photoluminescence microscope. The method is equivalent to using a standard optical microscope and provides a contactless means to measure charge (L) and spin (L_s) diffusion lengths. The measured values of L and L_s are in excellent agreement with the spatially averaged polarization and a sharp reduction in these two quantities (L from 21.3 mum to 1.2 mum and L_s from 1.3 mum to 0.8 mum) is measured with increasing surface recombination. Outwards diffusion results in a factor of 10 increase in the polarization at the excitation spot.