PHOTOLUMINESCENCE AND FREE-CARRIER INTERACTIONS IN ERBIUM-DOPED GAAS

The photoluminescence properties of GaAs:Er doped with a new pyrazole and pyridine-based Er source, tylpyrazolato)bis(4-tert-butylpyridine)e rbium(III) were investigated. These samples showed significantly stron ger and sharper 1.54 mu m Er3+ luminescence than in GaAs:Er samples do ped with cyclopentadienyl-based Er sources. The efficient luminescence was associated with the Er-2O center, formed with unintentional oxyge n impurities. The Er3+ emission was greatly reduced in n-type samples, whereas the emission remained strong in p-type samples. This trend su ggests that either the free hole concentration is very important to th e Er3+ excitation efficiency, and/or there is a strong Auger quenching mechanism which involves free electrons. A model based on the results of a two-beam experiment indicates the presence of strong Auger energ y transfer from the Er-bound exciton to a free electron. Auger energy transfer from the excited Er3+ ion to a free electron was found to be much less important. The temperature dependence of the Er3+ emission w as also examined. A decrease in intensity was observed at the lowest t emperatures. This effect was attributed to the freeze-out of carriers onto a relatively shallow trap which could be related to either Er or shallow accepters. (C) 1998 American Institute of Physics.