Determination of InP surface state density distribution from excitation-power-dependent photoluminescence spectra using genetic algorithm-based fitting procedure

The energy distribution of the surface state density NSS(E) on the n-type InP surface was determined from a rigorous computer analysis of the dependence of the band-to-band photoluminescence efficiency (YPL) versus excitation light intensity (Φ). The analysed experimental YPL–Φ spectrum, taken from the literature, was obtained at room temperature for the chemically polished n-InP(1 0 0) surface. The theoretical values of YPL were calculated using a numerical simulator, taking account of all possible bulk and surface recombination processes. We reproduced very well the experimental YPL–Φ dependence, which exhibited a strong increase of YPL. We also determined the continuous U-shaped NSS(E) distribution from the best fit to the experimental data by applying a novel fully-computer procedure based on genetic algorithm. Furthermore, we found that the surface non-radiative recombination dominates over the bulk recombination channels (in terms of recombination rates), and governs the behaviour of radiative recombination versus Φ.