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After an Si oxide layer of 3 nm thickness had been grown by using magnetron sputtering on a p-type Si (100) substrate, an indium tin oxide (ITO) film was deposited onto the Si oxide layer by using electron beam deposition. Electroluminescence (EL) from such an ITO/Si oxide/p-type Si structure was measured under a forward bias of 5 V or more. Its EL power efficiency is about eight times as large as that of a semitransparent Au/Si oxide (3 nm)/p-Si structure. The experimental results indicate that the greater EL power efficiency is due not only to the higher optical transparency of the ITO film compared with Au film in a range of 300 to 900 nm, but also to some new luminescence centers introduced in the Si oxide layer during the ITO deposition process.

We have studied the effects of γ-ray irradiation on electroluminescence (EL) from Au/extra thin Si-rich SiO2 film/p-Si Structures. After γ-ray irradiation, for the structure with a 600°C annealed Si-rich SiO2 film a new blue EL band with a peak at around 480 nm was observed, and for the structure with a 300°C annealed Si-rich SiO2 film the red EL band shifts from 670 to 660 nm and its intensity and full width at half maximum increase pronouncedly. The experimental results demonstrate that the defects induced by γ-ray irradiation are responsible for the blue EL band as well as for the variations of the red EL band.