Zeeman spectroscopy of an axial-double-acceptor bound exciton in GaAs grown by molecular-beam epitaxy.

Abstract

Zeeman-, resonant-, and polarization-spectroscopic investigations of an exciton bound to an axial, double-acceptor-type defect in gallium arsenide grown by molecular-beam epitaxy are presented. With nonresonant excitation, two bound-exciton recombination lines, ${\mathit{Y}}_{1}$ and ${\mathit{Y}}_{1}^{\mathrm{*}}$ appear in the near-gap region. Selective excitation of ${\mathit{Y}}_{1}$ and ${\mathit{Y}}_{1}^{\mathrm{*}}$ reveals 1s, 2s, and 3s two-hole replicas consistent with the presence of two holes in the bare neutral complex. The ionization energy of the first hole is calculated to be 214 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ (26.5 meV)---almost equal to the effective-mass value. ${\mathit{Y}}_{1}$ and ${\mathit{Y}}_{1}^{\mathrm{*}}$ are polarized along the [1\ifmmode\bar\else\textasciimacron\fi{}10] and [110] directions, respectively. The anisotropy of the Zeeman splittings also demonstrates preferential incorporation of the defect along the [110] crystallographic axis. A spin Hamiltonian containing three free parameters is used to model the Zeeman measurements.