Visible photoluminescence from a-Si:H/SiO2 superlattices fabricated by UHV evaporation

Hydrogenated amorphous-Si/SiO2 (a-Si:H/SiO2) superlattices with different a-Si:H thickness in the range of a few nanometers have been fabricated by ultra high vacuum evaporator (UHV evaporator). The photoluminescence (PL) of our superlattices is observed in the visible spectral region and the peak energy shifts to higher energy as the a-Si: H layer thickness decreases. The temperature dependence of the PL spectra reveals four sub-bands by fitting. Bands at 2.2, 1.9, 1.65 and 1.45 eV are detected and are attributed to E 'delta centers, nonbridging-oxygen-hole centers (NBOHC), Si/SiO2 interface and a-Si:H layer, respectively. We explain the overall blueshift of the PL spectra by the modification of the contribution of these sub-bands. (C) 1999 Elsevier Science B.V. All rights reserved.