Smart Wide‐Bandgap Omnidirectional Reflector as an Effective Hole‐Injection Electrode for Deep‐UV Light‐Emitting Diodes

Abstract Deep‐ultraviolet light‐emitting diodes (DUV‐LEDs) find widespread applications in various industries and are a focus area in environmental and life science research. However, the quantum efficiency of DUV‐LEDs is still low because of the unbalanced hole injection, high operation voltage, and low reflectivity of the p‐electrode. In this study, a smart wide‐bandgap omnidirectional reflector (ODR), which simultaneously acts as an effective hole‐injection electrode, is demonstrated for a flip‐chip DUV‐LED. The smart ODR is composed of p‐type AlGaN (p‐AlGaN)/Ni:AlN/Al with a high reflectivity of 94.2% at 280 nm, in which AlN with a theoretically calculated thickness of 40 nm is Ni‐doped using the pulsed electrical breakdown (PEBD) method. The smart ODR‐mounted AlGaN‐multiquantum‐well‐based DUV‐LED exhibits a remarkable wall‐plug efficiency (4.8%) and high external quantum efficiency (8.5%) at a low operation voltage of 9.75 V owing to the fused layer of Ni₃N and Ga vacancies formed in the interfacial region of the p‐AlGaN and AlN layers, through the mutual diffusion of Ni and Ga during PEBD. The interface‐mediated Ohmic contact leads to an effective hole injection without reducing the reflectivity, yielding increased optical output and electric input powers. The proposed smart ODR can provide an innovative route for the manipulation of DUV light.