Light-activated photoluminescence of porous silicon

摘要

Abstract: Samples of porous silicon (PS) were etched in concentrated hydrofluoric acid. The initial and etched samples were exposed to the air by pairs at room temperature either in the dark or in daylight. In the process of exposition the integrated intensity of photoluminescence (I$-PL$/) excited by a nitrogen laser (337 nm) was measured in regular time intervals on all samples. It has been established that when samples are exposed to the light their I$-PL$/ rises with time, increasing more rapidly in the etched samples than in the nonetched ones. I$-PL$/ of the etched samples flattened out after several weeks, while that of the nonetched ones - after several months. I$-PL$/ of the samples that were in the dark practically did not change with time. It is shown that the rate of I$-PL$/ rise depends on a degree of ionization of the air where the samples were located. The results obtained confirm the idea that one of the main factors limiting the quantum yield of PS photoluminescence is the nonradiative recombination that results from the presence of dangling bonds which may be saturated by the light-generated air ions.!14