Wide-gap a-C:H prepared by dc glow discharge of CH4: photoluminescence and electroluminescence in the visible region

We report on visible electroluminescence from metal–semiconductor–insulator–semiconductor–metal heterostructures employing a wide-gap insulating amorphous carbon (a-C:H) film. The a-C:H layers were prepared by dc glow discharge decomposition of methane (CH4). The electroluminescence is due to combined effects of surface and volume phenomena, namely to the radiative decay of surface plasmons excited at the positively biased electrode, and the radiative recombination of electron–hole pairs across the forbidden gap of the active layer. The surface- and bulk-related emissions are peaked at ∼750 and ∼600 nm, respectively. Thermal annealing of the samples, up to ∼200 °C, increases significantly the total electroluminescence efficiency, by one order of magnitude, due to an improvement of volume phenomenon in the emission process.