Optical transitions in GaAs:Fe studied by Fourier-transform infrared spectroscopy

Abstract

A high-sensitivity Fourier-transform emission and absorption technique has been used to study the iron-related optical transitions in GaAs. Improved photoluminescence and absorption spectra between 2500 and 3500 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ allow a detailed analysis of the four routinely observed zero-phonon lines corresponding to the $^{5}$${\mathit{T}}_{2}$${\ensuremath{\rightarrow}}^{5}$E internal transitions within the $^{5}$D ground state of ${\mathrm{Fe}}^{2+}$ in tetrahedral environment, and of the corresponding phonon and vibrational sidebands. We derived a rather complete level scheme of the $^{5}$D sublevels at ${\mathrm{Fe}}^{2+}$ in GaAs from the transition energies found in absorption spectra recorded at higher sample temperatures in the energy range between 2900 and 3400 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. Some of the excited states were found to be significantly lowered by dynamical Jahn-Teller contributions. The iron-related line labeled 1a, which has now also been observed in absorption, is tentatively ascribed to a ${\mathrm{Fe}}^{3+}$ transition $^{4}$${\mathit{T}}_{1}$${\ensuremath{\rightarrow}}^{6}$${\mathit{A}}_{1}$.