Leakage current origins and passivation effect of GaN-based light emitting diodes fabricated with Ag p-contacts

The origins of leakage currents and passivation effects of GaN-based light emitting diodes fabricated with Ag p-contacts have been investigated by electrical measurements. A significant increase in reverse leakage current is attributed to the surface migration of Ag. A passivation of mesa sidewalls by SiO2 is found to be effective in suppressing the reverse leakage. However, the passivation results in a somewhat increase in the forward leakage at moderate voltages. Such forward leakage is explained in terms of the presence of local deep-level states in p-GaN generated during SiO2 deposition, acting as a parasitic diode with a lower barrier height. (C) 2008 American Institute of Physics.