J. Koshka et al., ACTIVATION OF LUMINESCENCE IN POLYCRYSTALLINE SILICON THIN-FILMS BY ULTRASOUND TREATMENT, Applied physics letters, 69(17), 1996, pp. 2537-2539
A dramatic increase of infrared photoluminescence (PL) intensity by a
factor of 2 orders of magnitude is observed after a few minutes at 250
degrees C of ultrasound treatment (UST) applied to polycrystalline si
licon thin films on glass substrates. In films obtained by solid-phase
crystallization of amorphous silicon at 550 degrees C, UST enhances t
he PL band intensity at 0.7 eV, and also activates a new luminescence
maximum at about 0.9 eV. We prove that the 0.9 eV PL band is related t
o the amorphous fraction of poly-Si films. Due to similarities in spec
tral shape and temperature behavior, this UST activated luminescence i
s attributed to a ''defect'' PL band previously observed in hydrogenat
ed amorphous Si. This conclusion is confirmed by using a set of films
with controlled fractions of the amorphous to crystalline phase. A mec
hanism of ultrasound stimulated hydrogen detrapping followed by hydrog
en diffusion and passivation of nonradiative centers (e.g., dangling b
onds) in polycrystalline and amorphous Si films is discussed. (C) 1996
American Institute of Physics.