| In this dissertation, the properties of photoluminescence (PL) and electroluminescence (EL) from Ge-Si02 thin films and mechanisms of light emission have been studied. Ge-Si02 thin films were deposited on Si substrates by radio frequency magnetron sputtering technique with a Ge-Si02 composite target. Films were annealed in N2 ambience for 30 mm at different temperature. The microstucture of films were characterized by several analysis techniques, such as XRD, TEM, FuR, XPS and so on. When annealed at temperature higher than 600C, Ge nanocrystals (nc-Ge) appeared in films. And they increased from 3.9 to 6.1 nm with the increase of annealing temperature from 600X2 to l000. Under ultraviolet excitation, all samples emit a strong violet band centered at 394nm. With the formation of nc-Ge, the samples exhibit another emission of orange band with the peak at 580nm and its intensity increases with the increasing size of nc-Ge. Analytical results indicate that the violet band comes from CeO defect and the orange band originates mainly from the luminescence centers at the interface between the nc-Ge and Si02 matrix. EL devices were fabricated based on 20-nm-thickness Ge-SiO., films and their structures are Au/Ge-Si02/p-Si and Au/Ge-Si02/n-Si. For comparison, Au/Si-SiO.,/p-Si structures were also made. For Au/Ge-Si02/p-Si and Au/Si-SiO,/p-Si structures, they emit EL peaked at 5lOnm when forward biases were greater than 6V and 6.5V, respectively, while no detectable light emission can be observed under reverse bias. But for Au/Ge-Si02/n-Si structure, EL can be obtained only under reverse bias. The EL is stable and reproducible and can be seen by naked eye. The results suggest that the generation of carriers result from bipolar injection and impact ionization by hot electrons for EL under forward and reverse bias, respectively. Although the progresses of carrier's generation are different for these two kinds of EL, the recombination of carriers is mainly via luminescence centers in Si02 matrix.
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