Correlation of electroluminescence with Ge nanocrystal sizes in Ge-SiO2 co-sputtered films

Ge-doped SiO2 films were deposited on p-Si substrates by magnetron sputtering and metal-insulator-semiconductor: (MIS) structures were fabricated with semitransparent An layers on SiO2 films. The MIS structures exhibit electroluminescence (EL) peaked at 590 nm. The positions of the EL peaks from the samples with different Ge nanocrystal sizes keep unchanged. The maximal peak intensity appears in the sample annealed at 600degreesC in N-2 atmosphere, in which the average size of Ge nanocrystals is about 4 nm. X-ray diffraction results show that the EL intensities are closely related to Ge nanocrystal sizes. Theoretical analyses suggest that the energy gaps of Ge nanocrystals relate with the discrepancy of EL intensities by influencing transport properties of carriers. Our experiments provide a possible avenue for improving the EL intensity, which will be more useful in optoelectronics. (C) 2002 Elsevier Science B.V. All rights reserved.