Porous Si1-xGex (PSiGe) layers with efficient room temperature visible phot
oluminescence (PL) were elaborated by anodical etching from p-type doped ep
itaxial layers with Ge contents from 5 to 30%. The luminescence is characte
rised by a broad PL band centred at 1.8 eV. Time resolved photoluminescence
decay is studied in porous silicon germanium as a function of germanium co
ntent, temperature, emission energies and surface passivation. The PL decay
line shape is well described by a stretched exponential in all cases. The
effective lifetime at low temperature in as prepared porous Si1-xGex is 400
mu s, i.e. an order of magnitude less than in porous silicon. After the fo
rmation of a 20 Angstrom thick oxide surface layer we observe a decrease of
the effective lifetime to 20 mu s at T = 4 K. (C) 1999 Published by Elsevi
er Science B.V. All rights reserved.