A study was made of up-conversion (anti-Stokes) photoluminescence in bulk material. It was found that both semi-insulating and conductive samples exhibited up-conversion photoluminescence. The latter was induced by a 2-step excitation process via deep defects. The excitation spectra provided valuable information concerning the defects which were involved. In the case of semi-insulating material, the results revealed 2 different defects. The initial up-conversion photoluminescence was completely quenched by irradiation with 1 light. The quenching phenomena and the shape of the excitation spectra connected the EL2 defect to the initial up-conversion photoluminescence. In the case of photo-quenched samples, another up-conversion photoluminescence was found. The latter had a threshold energy, at 1.3eV, which corresponded to emission by a BAs double acceptor. All of the conductive samples exhibited up-conversion photoluminescence features, without bleaching.

T.Iino, J.Weber: Materials Science Forum, 1995, 196-201, 993-1000