Mechanism of light production in metal-insulator-semiconductor diodes; GaN:Mg violet light-emitting diodes

The mechanism of electroluminescence in MIN GaN:Mg violet light-emitting diodes was analyzed by considering observed structural features of the diodes as well as their electrical and optical characteristics. Comparison of the observed I–V characteristic, including dependence upon temperature and upon film thickness, with all possible mechanisms for conduction in insulators lead to a proposed conduction mechanism of quantum mechanical tunneling, with the I–V characteristic being well represented by the Fowler-Nordheim equation. The proposed mechanism of light production involved impact ionization of luminescent centers near the i-n junction, with subsequent radiative recombination. This proposed mechanism was supported by measurements of carrier multiplication in the device and a steep voltage gradient at the i-n junction. The impact ionization process occurs in discrete regions coincident with sub-grain boundaries in the GaN film.