Computer analysis of photoluminescence efficiency at InP surface with U-shaped surface state continuum

Rigorous computer simulations of the dependence of the band-to-band photoluminescence quantum efficiency (Y_PL) were performed for n-type InP surfaces in a wide range of excitation light intensity, Φ (from 10¹⁸ to 10²⁵ cm^-2 s^-1). A strong influence of the density of surface states (N_SS) and their capture cross sections for electrons (σ_n) and holes (σ_p) on Y_PL-Φ dependencies was found. We reproduced very well the experimental dependence Y_PL-Φ, taken from the literature, for the chemically polished InP (1 0 0) surface, which exhibited strong increase of Y_PL. From the fitting of the experimental data we determined the surface state parameters, including the minimum density of U-shaped continuum (N_SS0 = 10¹¹ eV^-1 cm^-2), and capture cross sections (σ_n = 10^-14 cm² and σ_p = 10^-13 cm²). The best fitting was carried out using a fully-computer procedure based on a novel Simple-Genetic-Algorithm (SGA) concept. In addition, the behaviour of the effective surface recombination velocity (S_eff), and quasi-Fermi levels for electrons (E_Fn) and holes (E_Fp) was discussed.