Excitation and temperature quenching of Er-induced luminescence in a-Si:H(Er)

Photoluminescence (PL) and light absorption of Er-doped amorphous hydrogenated silicon are studied in the temperature range 77-300 K. In the linear pumping regime the intensity of the Er-induced luminescence decreases by a factor of about 15 in this temperature range. Frequency resolved spectroscopy shows that in the same temperature range the lifetime of the excited erbium ions in the amorphous matrix decreases by a factor of 2.5 only. Excitation spectroscopy proves that the primary step of the excitation mechanism is the absorption and free carrier generation in the amorphous matrix. The emission is excited effectively by subgap light in the range of the Urbach edge and even in the range of defect absorption. Based on these experimental findings we propose a defect-related Auger excitation (DRAE) mechanism of erbium luminescence. Probabilities of the DRAE and the competing radiative defect recombination processes (D-0+e-->D-) are calculated. It is shown that the probability of the DRAE process is larger by an order of magnitude. In this model the temperature quenching of the erbium luminescence observed above 200 K results from the competition of the DRAE and multiphonon nonradiative recombination at the defects.