Current crowding in deep ultraviolet light-emitting diodes with fish-bone shaped p-electrode by microscopic emission investigation

Current crowding is the main bottleneck preventing the prosperity of AlGaN-based deep-ultraviolet light-emitting-diodes (DUV-LEDs) considering the low electrical conductivity of p-type contact layer. A deeper understanding of the current distribution in p-AlGaN is critical, which enables the rational design of advanced device architectures. In this work, a fish-bone-shaped p-type electrode was deposited on top of a 280 nm AlGaN DUV-LED for investigation of localized emissions. A significantly raised junction temperature was identified, causing efficiency droop in DUV-LEDs under relatively low injection current with fish-bone-shaped p-type electrodes. High junction temperature is attributed to the significantly high localized current density which is confirmed by the spatial-resolved electroluminescence spectra and theoretical simulation. The crowding current level beneath the p-electrodes is estimated to be several times higher than that in between the electrodes.