Two ways of porous Si photoluminescence excitation

The mechanism of photoluminescence excitation (PLE) in porous silicon (PS) is studied. The investigation of the PS aging process by photoluminescence (PL), PLE, EPR, Auger, FTIR and SIMS methods show that two PLE bands correspond to different substances on a silicon wire surface. One of them is the species which is desorbed during aging with an activation energy ≈0.5–0.6 eV. The energy transfer from this species (absorption centers) to luminescence centers which may be located in Si wire, Si/SiO interface or silicon oxide, is supposed. The nature of this species is discussed. The second substance is silicon oxide, probably.