Investigation of Light-Extraction Efficiency of Flip-Chip AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes Adopting AlGaN Metasurface

Herein, we investigate the influence of an AlGaN metasurface on AlGaN-based deep-ultraviolet light-emitting diodes' light-extraction efficiency by utilizing the 3D finite-difference time-domain method. As the first step in this study, we optimize an AlGaN metasurface to maximize the transmittance from LED to air. Then, six different flip-chip structures' light-extraction efficiencies are compared with each other to judge the usefulness of the metasurface's adoption on AlGaN-based LED. Considered structures are classified into two categories, with and without inclined sidewall, respectively. Each classified structure is subdivided again by three factors: flat interface, roughed cones, and metasurface on n-AlGaN. Extracted results show that the combination of inclined sidewall and the AlGaN metasurface shows synergetic results positively increasing light-extraction efficiency.