Near-field optical spectroscopy has been used to study the photoluminescenc
e features of a porous silicon device at room temperature, with a subwavele
ngth space resolution of about 50-100 nm. In particular, a prototype of a p
orous silicon-based light-emitting diode has been characterized by imaging
morphology, near-field scattering intensity and emission maps of the same p
ortion of the sample with a space resolution of better than 60 nm. Structur
ed emitting centres are found on the porous regions with size ranging from
200 nm to 1 mu m. Emission features, acquired as near-field spectra as well
as emission maps at fixed wavelengths, provide crucial information on the
prototype structure at the nanometric level, exploitable for improvement in
production steps as well as for the study of the dominant working mechanis
ms of the device.