Long-time stability of photoluminescence in porous silicon

The long-term behavior of photoluminescence (PL) of porous silicon (PS) at room temperature (RT) and elevated temperatures was investigated in order t o assess the suitability of PS for commercial applications, which mostly re quire lifetimes of years. At higher storage temperatures (60-120 degrees C) the decay time t(1) of PL intensity is between 1.8 and 0.4 h. Surprisingly after approximately 20 days of storage at high temperature the PL intensit y recovers to a steady-state value of quantum efficiency QE = 2%, which is also approached when stored at room temperature. By oxidizing the samples t he QE is increased (to approx. 3%). From the extremely slow decay of PL aft er recovery, a decay time constant of t(3) approximate to 2000 days was est imated. For samples, that are permanently irradiated by UV light (1.5 mW/cm (2)), the decay time is shorter. Hence, with intermitting UV radiation life times of years can be expected. (C) 2000 Elsevier Science S.A. All rights r eserved.