The depth dependent photoluminescent response of hydrogen passivated and oxidized porous silicon

Silicon is at the foundation of many of our society's electronic devices. Porous silicon (pSi) is derived from silicon and can therefore be easily integrated into these devices. There are several promising application of pSi stemming from the photoluminescence (PL) under UV excitation which includes chemical sensing, electroluminescent displays, lasing materials, optoelectronics, and photo-detectors. The pSi PL stems from quantum confinement of silicon nanocrystallites that are created during the pSi fabrication process.;While the PL of silicon nanocrystallites is well understood the depth dependant PL of nanocrystallites located through out the pSi matrix is not. A large fraction of pSi PL studies have been carried out by using wide field measurement techniques which have no depth dependent information. The pSi PL has also been studied by using confocal techniques for their superior spatial resolution in the x and y planes but can also obtain information along the z axis for opaque materials like pSi.;We developed an exfoliation technique to remove bias from the crystalline silicon wafer (cSi). Confocal depth dependent PL measurements have revealed that the pSi (49% porosity) center is blueshifted from the top and bottom. By increasing the etching time and as a result the porosity, the PL gradually became more uniform. This study suggests that the pSi chemical surface initially had a spatial distribution of oxide and fluoride species that became more uniformly dispersed as the etching time increased. Oxidizing the pSi (49% porosity) caused the pSi bottom and a region towards the center to oxidize to a greater extent. Together this information supports our conclusion that the pSi chemical surface is not homogenous along the z axis.