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.