LOW-TEMPERATURE FATIGUE OF PHOTOLUMINESCENCE IN AGED POROUS SILICON

We present a photoluminescence (PL) fatigue study at liquid helium tem peratures in mesoporous and microporous silicon (PSi) layers impregnat ed in air. In contrast to PL measurements at room temperature, at low temperatures no recovery of the PL is observed. The results show that the infrared (IR) and slow-luminescent visible (S) band display differ ent behaviors under prolonged illumination. In the S band, similar dep endencies in both kinds of specimens are observed with much stronger f atigue strength on the high energy side, revealing that this band is p ossibly composed of two different kinds of luminescent species. This i dea is further supported by the measured change of the luminescence in tensity and of the non-exponential PL decay at different photon energi es. By analogy with the well-known photo-induced effect in CdSSe micro crystallites, photo-ionization may be responsible for the PL fatigue.