VISIBLE ROOM-TEMPERATURE PHOTOLUMINESCENCE FROM OXIDIZED GERMANIUM

Strong visible photoluminescence (PL) has been observed at room temper ature from oxidized amorphous hydrogenated germanium. Excitation by th e 488 nm line from an argon ion laser yields a brood PL peak at 2.2 eV with a full-width-half-maximum (FWHM) of 0.5 eV. The luminescence int ensity depends on the morphology of the untreated a-Ge:H film produced by plasma enhanced chemical vapor deposition (PECVD). Films ranging f rom ones with coarse columnar microstructure and poor photoelectronic properties to ones with microstructure similar to that of device-quali ty a-Si:H were intentionally chosen. After oxidation in air at 500 deg rees C for one hour, the films with coarse microstructure yield the hi ghest luminescence intensity, comparable to that from porous silicon, while the best films with minimum microstructure yield orders of magni tude lower intensity, Removing the germanium oxide from the film reduc es the luminescence intensity. Powder-like Ge was also produced by the rmal evaporation in 0.3 Torr of argon. After annealing in air at 500 d egrees C for two hours strong PL is observed with peak position and sp ectral width similar to those from oxidized poor PECVD a-Ge:H and comm ercial GeO2.