CHARACTERIZATION OF A POROUS SILICON DIODE WITH EFFICIENT AND TUNABLEELECTROLUMINESCENCE

Electrical and optical properties of electroluminescent porous silicon pn diodes have been investigated. The measurements were performed und er pulsed conditions to maintain high quantum efficiency (similar to 0 .2%) operation. Diodes with different peak wavelengths, obtained by va rying the etching parameters, were used. A high correlation between el ectroluminescence (EL) and photoluminescence (PL) of porous silicon (P Si) structures was observed: similar luminescence peak position, spect ral width, quantum efficiencies, decay time constants, and luminescenc e quenching at increasing temperature, suggesting the same recombinati on mechanism for both EL and PL. The temperature dependence of the for ward current and EL revealed a thermally activated conduction mechanis m with an activation energy of similar to 0.1-0.2 eV which is attribut ed to potential barriers in the undulating silicon wires. EL quenching and a redshift of the EL peak at an increased temperature were also o bserved. This is attributed to shorter nonradiative lifetimes and a th ermally enhanced escaping of carriers from ''active'' crystallites. Fi nally, exhausting of the EL during long pulse durations has been chara cterized and we propose a charging mechanism in the PSi network as a p ossible origin. (C) 1996 American Institute of Physics.