Characterization of a porous silicon diode with efficient and tunable electroluminescence

Electrical and optical properties of electroluminescent porous silicon pn diodes have been investigated. The measurements were performed under pulsed conditions to maintain high quantum efficiency (similar to 0.2%) operation. Diodes with different peak wavelengths, obtained by varying the etching parameters, were used. A high correlation between electroluminescence (EL) and photoluminescence (PL) of porous silicon (PSi) structures was observed: similar luminescence peak position, spectral width, quantum efficiencies, decay time constants, and luminescence quenching at increasing temperature, suggesting the same recombination mechanism for both EL and PL. The temperature dependence of the forward current and EL revealed a thermally activated conduction mechanism with an activation energy of similar to 0.1-0.2 eV which is attributed to potential barriers in the undulating silicon wires. EL quenching and a redshift of the EL peak at an increased temperature were also observed. This is attributed to shorter nonradiative lifetimes and a thermally enhanced escaping of carriers from ''active'' crystallites. Finally, exhausting of the EL during long pulse durations has been characterized and we propose a charging mechanism in the PSi network as a possible origin. (C) 1996 American Institute of Physics.