THEORY OF THE PHOTOLUMINESCENCE SPECTRA OF POROUS SILICON

Porous silicon (PS) with its distribution of crystallite sizes is a hi ghly disordered material. We present a theoretical formulation to expl ain the photoluminescence (PL) spectra of porous silicon. We base our formalism on the quantum confinement model using methods similar to th ose of Kane and Lifshitz. A minimal set of parameters is employed whos e numerical values are obtained from independent experiments and/or mi croscopic theories. Our work demonstrates (i) a downshift in the PL pe ak due to the size distribution, thus facilitating the use of smaller and physically reasonable excition binding energy; (ii) a PL spectrum with a line-shape asymmetry on the energy scale, having a full width a t half maximum of congruent-to 350 eV, in consonance with experiments; (iii) the presence of both columns and dots in PS; (iv) the presence of local inhomogeneities. Modifications of our model and extensions to related experimental phenomena are also discussed.