AN INVESTIGATION OF THE POROUS SILICON OPTICAL-ABSORPTION POWER-LAW NEAR THE BAND-EDGE

A theoretical investigation of the absorption coefficient of p-type do ped porous silicon near the band edge is presented. We assume that the absorption coefficient is constructed by taking an average over a dis tribution (in terms of band gap) of absorption coefficients of individ ual crystallites. Exploiting physics fundamental to the crystallite op tical absorption process, we derive the relation between the absorptio n coefficient and the averaged conduction density of states near the b and edge for porous silicon. By postulating a specific form for the ef fective conduction density of states we find excellent agreement with recent optical absorption data for p-type doped porous silicon. We att empt to explain the basis for this postulate phenomenologically by sug gesting a certain large-scale behaviour of the particle size distribut ion. The implication of further experimental verification will be disc ussed.