The effects of impurities upon photoluminescence and optically induced paramagnetic states in chalcogenide glasses

Abstract

Photoluminescence (PL) and optically induced electron spin resonance (ESR) have been studied in As 2Se 3 glasses doped with Cu, Tl, I, Ag, In, and K and in B-doped As 2S 3 glass. In all cases there is no significant change in PL efficiency or intensity of induced ESR until dopant concentrations exceed ∼1 at.%. These results are in marked contrast the strong dependence of transient hole transport upon dopant concentration in the same glasses. These parallel but contrasting observations are discussed in terms of the predicted effects of dopants on defects in chalcogenide glasses postulated by Mott on the basis of the charged defect model of Mott, Davis and Street (MDS). PL and ESR studies of the AsSe glass system have revealed that oxygen contamination can severely quench PL efficiency and ESR intensity for As concentrations <1 at.%. The PL efficiency of high purity Se glass is shown to be approximately a factor of 10 higher than previously reported for nominally pure Se. In such high purity glassy Se, the addition of As dopants produces essentially no change in the PL until the As concentration exceeds ∼0.1 at.%. These results are consistent with the existence of twodistinctly different PL bands, one centered at 0.8 eV and characteristic of some defect in pure Se, and one centered at ∼0.9 eV which is produced by the introduction of As atoms. Within the framework of the MDS model these results appear to indicate a negatively charged defect (D −) as the PL center in pure Se.