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Analysis of the decay of picosecond fluorescence in semiconductors

1985; Elsevier BV; Volume: 185; Issue: 2 Linguagem: Inglês

10.1016/0368-1874(85)80130-1

2590-2954

Stephen W. Feldberg, Moshe Evenor, D. Huppert, S. Gottesfeld,

Silicon Nanostructures and Photoluminescence

When an exponential profile of electron-hole pairs is photogenerated (in a semiconductor) with a delta-function light pulse, unequal diffusion coefficients of holes and electrons (i.e. De≠ Dh) effect deviations from electroneutrality as electrons and holes diffuse into the bulk semiconductor. These deviations will in turn effect errors in the analysis of data (e.g. time resolved fluorescence) when using theory based on the presumption of electroneutrality. We deduce here the experimental conditions required for an effective electroneutrality to be maintained during the course of an experiment. Analyses were carried out using computer simulations without the presumption of electroneutrality and the analytic solution with the presumption of electroneutrality. The differences in the measured fluorescences predicted by the two computations are characterized as a function of a variety of experimental parameters and physical properties: intensity (of the excitation pulse), the absorption of the exciting and emitted light, the the ratio Dh/De, bulk dielectric constant of the semiconductor, bulk and surface recombination kinetics. It is shown that a conditon of adequate electroneutrality can be effectively attained when a well defined a minimum number of electron-hole pairs is generated; an upper limit of the number of e−–k+ pairs is also established in order to avoid an intolerable temperature pulse.