Enhancing light extraction efficiency of 242 nm DUV micro-LEDs via hybrid nanorod arrays
Licai Zhu, Shunpeng Lv, Ke Jiang, Jianwei Ben, Shanli Zhang, Jialong Hao, Jiale Peng, Ruojia Zhang, Dabing Li, Sun Xiaojuan
Abstract
Deep-ultraviolet (DUV) micro-LEDs are pivotal for applications such as maskless lithography and germicidal disinfection. However, improving light extraction efficiency (LEE) remains a significant challenge. This study presents a novel, to the best of our knowledge, strategy to enhance LEE by employing gold thin-film annealing and dry-etching techniques to fabricate disordered p-GaN/p-AlGaN hybrid nanorod arrays. The enhancement mechanism involves directly reflecting the transverse electric (TE) mode within the escape cone at the p-AlGaN/Al mirror interface, thereby minimizing absorption by p-GaN. Simultaneously, TE and transverse magnetic (TM) modes outside the escape cone are scattered by the nanorods and redirected into the escape cone, promoting forward emission. 3D finite-difference time-domain simulations predict a 79% increase in LEE for TM and a 187% improvement for TE. Experimentally, we observe a 140% enhancement in peak light output power (LOP), a 148% boost in external quantum efficiency (EQE), and a 146% increase in wall-plug efficiency (WPE) at 1 mA compared to planar designs. This innovative approach markedly advances the performance of DUV micro-LEDs, fostering new possibilities in high-efficiency DUV technologies.