Efficiency boosting of 236 nm AlGaN-based micro-LEDs

In this study, 236 nm AlGaN-based deep ultraviolet (DUV) micro-LEDs with different sized P-contact areas are designed and fabricated, and the sidewalls are restored by a wet chemical treatment method with KOH solution. The results reveal that proper KOH treatment can effectively remove plasma damaged materials and clearly show the formation of m -plane facets. Compared with untreated micro-LEDs, the reverse leakage current of the treated micro-LEDs under −10 V decreases by up to 91.7% and the specific contact resistivity (SCR) reduces from 6.94 Ω cm 2 to 0.07 Ω cm 2 . The underlying mechanism is that the KOH treatment removes the sidewall defects which lead to surface nonradiative recombination sites and surface leakage. Moreover, KOH treatment also removes contamination on the P + -GaN surface and leads to lower SCR. However, a much longer treatment also destructs the 20 nm P + -GaN layer, which results in higher voltage but less DUV light absorption. As a result, the peak light output power density increases from 2.12 W cm −2 to 4.01 W cm −2 , representing an 89.2% increase. Efficient enhancement of micro-LEDs is anticipated to facilitate the development of DUV micro-LEDs for maskless lithography and high-capacity DUV non-line-of-sight communication.