Temperature dependence of photoluminescence in porous silicon and its interpretation using the porous-cluster model

Photoluminescence (PL) of porous silicon in the redband is studied at temperatures from 15 to 293 K. With increasing temperature, the PL spectrum peak redshifts and the width narrows, while the PL intensity increases until {~}70 K and then decreases slightly. At 293 K, the PL at higher emission energy decays faster with a broader rate distribution. The PL decay gets slower upon cooling, and becomes independent of emission energy below {~}70 K. These results are qualitatively interpreted using a porous-cluster model that assumes random vacancy sites in a Si lattice. The low-temperature PL can be explained by carrier recombination through localized states which are distributed in energy, and dimensionally disordered. The changes in the PL with temperature, on the other hand, are understood by thermal activation of recombination processes, including hopping of carriers among distributed localized states.