Er-luminescence in MBE-grown AlGaAs

Er-doped AlGaAs samples were grown by the MBE technique with concentrations of Er in the range 10¹⁸- 2 ×10¹⁹ cm^-3. Photoluminescence (PL) of Er³⁺ ions and Er-induced defects was studied at liquid helium and higher temperatures. From high resolution PL spectra the existence of three types of Er centers is deduced which differ by positions of fine structure lines, PL lifetimes, and temperature dependence. Our results indicate that these centers are accompanied by the appearance of three types of carrier traps with binding energies of 20, 50 and about 400 meV, respectively. Our experiments show evidence that carriers captured into these traps control the Auger excitation of Er ions assisted by multiphonon emission of local phonons. Temperature quenching of erbium luminescence is controlled by depopulation of defect states in the case of Auger excitation via the most shallow hole trap (20 meV) and by competition of multiphonon nonradiative capture with the Auger transitions in the case of the deepest defect (400 meV). Besides erbium luminescence at 1.54 μm, we have observed luminescence of erbium ions from upper excited states at 0.82 and 0.98 μm which demonstrates the possibility to realize a three-level scheme of light emission.