Spin-dependent recombination and hyperfine interaction at the deep defects

TL;DR

This paper develops a theoretical model for spin-dependent recombination at deep defects, incorporating hyperfine interactions, and analyzes how nuclear and electron spins influence optical polarization and photoluminescence.

Contribution

It introduces a reduced set of rate equations for electron-nuclear spin dynamics considering axial symmetry, applicable to arbitrary nuclear spin values.

Findings

Polarization and photoluminescence depend on excitation power with bell-shaped curves.

Nuclear spin relaxation significantly affects spin polarization.

The theory explains experimental observations of spin-dependent optical phenomena.

Abstract

We present a theoretical study of optical electron-spin orientation and spin-dependent Shockley-Read-Hall recombination taking into account the hyperfine coupling between the bound-electron spin and the nuclear spin of a deep paramagnetic center. We show that the number of master rate equations for the components of the electron-nuclear spin-density matrix is considerably reduced due to the restrictions imposed by the axial symmetry of the system under consideration. The rate equations describe the Zeeman splitting of the electron spin sublevels in the longitudinal magnetic field, the spin relaxation of free and bound electrons, and the nuclear spin relaxation in the two defect states, with one and two (singlet) bound electrons. The general theory is developed for an arbitrary value of the nuclear spin I, the magnetic-field and excitation-power dependencies of the electron and nuclear spin polarizations are calculated for the particular value of I = 1/2. The role of the nuclear spin relaxation in each of the both defect states is analyzed. The circular polarization and intensity of the edge photoluminescence as well as the dynamic nuclear spin polarization as functions of the excitation power are shown to have bell-shaped forms