Two-dimensional intensity distribution of photoluminescence from porous silicon

Photoluminescent (PL) intensity-distribution images and PL spectra of porous silicon (PS) have been analyzed. The PL intensity of the top surface of n-type PS is nearly uniform and is dependent upon illumination conditions during anodization. N-type PS fabricated under high power illumination has the peak of the PL spectra at shorter wavelength than that under low power illumination. On the other hand, the peak position of the PL spectra of n-type PS does not shift significantly with change of current density. The PL intensity of n-type PS is the maximum at the surface and decreases exponentially towards the Si substrate, P-type PS has a relatively broad intensity peak within the PS layer with or without illumination during fabrication. These results suggest that illumination during fabrication plays a role in the PL light emission of PS.