Photoluminescence-excitation analysis of Er-doped GaAs grown by metalorganic vapor phase deposition

Er-doped GaAs grown by metalorganic chemical vapor deposition was studied by photoluminescence and photoluminescence excitation (PLE) measurements using a color center laser that provides tunable light in the 1450–1550 nm range. The light in this wavelength region can directly induce the 4I15/2→4I13/2 intra-4f-shell transition of Er3+ ions. The PLE spectra of a specific Er center formed by oxygen codoping under suitable growth conditions were conclusively assigned by site-selective spectroscopy. Non-site-selective PLE spectroscopy, on the other hand, revealed that the atomic configurations of Er3+ ions change according to the Er concentration, growth temperature, and oxygen codoping. Sharp lines related to Er3+ ions with well-defined atomic configurations, and inhomogeneously broadened structures related to aggregates of Er3+ ions, are evident in the PLE spectra. The PLE spectra due to the direct intra-4f-shell excitation also revealed semiquantitatively that there are Er centers that do not show luminescence under above-band gap photoexcitation, because of low energy transfer efficiency from the host.