Upconversion induced by deep defects in GaAs

We have studied the upconversion (anti-Stokes) photoluminescence (UPL) in bulk-grown GaAs. Both semi-insulating (SI) and conductive GaAs exhibit UPL. The UPL is induced by a two-step excitation process via deep defects. Excitation spectra give valuable information about the involved defects. In SI GaAs, the results reveal two different defects. The initial UPL is quenched completely by irradiation of 1 mu m light. The quenching phenomena and the spectral shape of the excitation spectra connect the EL2 defect with the initial UPL. In photo-quenched samples, another UPL is found. The latter UPL has a threshold energy at 1.3 eV which corresponds to the emission energy by BA, double acceptor. All of the studied conductive samples exhibit UPL features without bleaching phenomena.