Significant Enhancement of Light Extraction in AlGaN-Based Deep-UV LED Through Ag-Nanodot/Ti/Al Reflective p-Contacts With an Ultra-Thin Ti Barrier

AlGaN-based deep ultra-violet (DUV) LEDs, which emit in the 200–280 nm range, hold great promise for applications in water and air purification, sterilization, and medical diagnostics while light extraction efficiency (LEE) is a primary bottleneck for improving the overall efficiency of deep-ultraviolet light-emitting diodes (DUV LEDs). In this study, guided by finite-difference time-domain (FDTD) simulations, we designed and fabricated Ag-nanodot/Ti/Al reflective p-contacts with an ultra-thin Ti barrier for DUV LEDs. The results demonstrated a 36% increase in wall plug efficiency (WPE) while maintaining good ohmic contact when Ti thickness decreased from 100 to 5 nm. Scanning electron microscope (SEM) analysis revealed the robust stability of the contact structure. The WPE (@51.7 A/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sup>, 40 mA) and LEE of the DUV LEDs with Ag-nanodot/Ti/Al p-contacts of 5-nm-thick Ti reached 4.42% and 9.575%, respectively. The results highlight the importance of p-contact reflectivity in achieving high-efficiency DUV LEDs and demonstrate a feasible route for improving the light output power (LOP) of DUV LEDs. This involves optimizing the reflector through metal-composite engineering, guided by FDTD simulations.