Optical absorption and photoluminescence of glow-discharge amorphous Si:F films

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Abstract
Optical absorption and photoluminescence (PL) spectra of fluorinated and hydrogenated glow-discharge amorphous silicon films were measured in the photon-energy range 0.7≤hν≤3.0 eV. The optical absorption spectra of the fluorinated samples are red shifted by about 0.3 eV, and their band-tail PL peak is red shifted by about 0.4 eV relative to the spectra of hydrogenated samples deposited under similar plasma conditions. Annealing of the a-Si:F samples increases their spin density and brings up the PL defect peak at 0.6–0.7 eV, without any significant shift of either the optical-absorption edge or the band-tail PL peak. The similarities and differences in the roles of fluorine and hydrogen in the amorphous silicon matrix are discussed.