Electrical quenching of photoluminescence from porous silicon

We have studied the visible photoluminescence (PL) of porous silicon (PS) under the condition that a bias voltage is applied in the direction of the PS layer thickness. It is shown, for the first time, that the PL intensity is sharply decreased when increasing the voltage. This electrical PL quenching was completely reversible. This phenomenon is interpreted as to arise from field-enhanced tunneling of carriers between silicon crystallites. The result presented here strongly suggests that the visible luminescence of PS is not based on electronic transitions in some molecular substance, but on the radiative recombination in Si nanocrystallites.