EXCITATION AND TEMPERATURE QUENCHING OF ER-INDUCED LUMINESCENCE IN A-SI-H(ER)

Photoluminescence (PL) and light absorption of Er-doped amorphous hydr ogenated silicon are studied in the temperature range 77-300 K. In the linear pumping regime the intensity of the Er-induced luminescence de creases by a factor of about 15 in this temperature range. Frequency r esolved spectroscopy shows that in the same temperature range the life time of the excited erbium ions in the amorphous matrix decreases by a factor of 2.5 only. Excitation spectroscopy proves that the primary s tep of the excitation mechanism is the absorption and free carrier gen eration in the amorphous matrix. The emission is excited effectively b y subgap light in the range of the Urbach edge and even in the range o f defect absorption. Based on these experimental findings we propose a defect-related Auger excitation (DRAE) mechanism of erbium luminescen ce. Probabilities of the DRAE and the competing radiative defect recom bination processes (D-0+e-->D-) are calculated. It is shown that the p robability of the DRAE process is larger by an order of magnitude. In this model the temperature quenching of the erbium luminescence observ ed above 200 K results from the competition of the DRAE and multiphono n nonradiative recombination at the defects.