Radiative properties of multi-carrier bound excitons in GaAs

TL;DR

This paper develops a formalism to predict and experimentally verify multiple radiative lifetimes of bound excitons in GaAs, accounting for symmetry, strain, and spin effects, with implications for semiconductor optoelectronics.

Contribution

A new formalism for predicting optical properties of multi-carrier excitons in various symmetry environments, validated by experiments on GaAs acceptor bound excitons.

Findings

Three distinct exciton lifetimes predicted and confirmed in GaAs.

Measured lifetimes are approximately 0.61 ns, 1 ns, and 0.75 ns.

Estimated intra-level and inter-level spin relaxation rates.

Abstract

Excitons in semiconductors can have multiple lifetimes due to spin dependent oscillator strengths and interference between different recombination pathways. In addition, strain and symmetry effects can further modify lifetimes via the removal of degeneracies. We present a convenient formalism for predicting the optical properties of ${k=0}$ excitons with an arbitrary number of charge carriers in different symmetry environments. Using this formalism, we predict three distinct lifetimes for the neutral acceptor bound exciton in GaAs, and confirm this prediction through polarization dependent and time-resolved photoluminescence experiments. We find the acceptor bound-exciton lifetimes to be ${T_o (1,3,3/4)}$ where ${T_o = (0.61 \pm 0.12) \text{ns}}$. Furthermore, we provide an estimate of the intra-level and inter-level exciton spin-relaxation rates.