Photoluminescence (PL) spectra of porous silicon (PS) at 77-440 K have
been studied. We report the observation of additional peaks on the PL
band and pronounced fine structure at rather high temperature (77 K)W
e have found the transformation of the spectra when as-prepared green-
emitting PS was subjected to drying in ambient air. The temperature qu
enching of the PL intensity revealed the same activation energy as the
electroconductivity, similar to 0.3 eV, and is considered to be the i
onization energy of the radiative centre. Optical absorption measureme
nts reveal the Urbach-like behaviour of the fundamental absorption edg
e and the energy gap, the latter being similar to 2.4 eV.