Smart Wide‐Bandgap Omnidirectional Reflector as an Effective Hole‐Injection Electrode for Deep‐UV Light‐Emitting Diodes. Issue 2 (26th November 2019)

• Record Type: Journal Article
• Authors: Lee, Tae Ho; Park, Tae Hoon; Shin, Hee Woong; Maeda, Noritoshi; Jo, Masafumi; Hirayama, Hideki; Kim, Bo‐Hyun; Kim, Tae Geun
• Is Part Of: Advanced optical materials. Volume 8:Issue 2(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-11-26
• Subjects: deep ultraviolet -- light‐emitting diodes -- omnidirectional reflectors -- pulsed electrical breakdown; Optical materials -- Periodicals; Photonics -- Periodicals; 620.11295
• DOI: 10.1002/adom.201901430
• Languages: English
• ISSNs: 2195-1071

Abstract

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 Ni3 N 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. Abstract : Smart wide‐bandgap omnidirectional reflector (ODR) is demonstrated as a hole‐injection electrode for a flip‐chip deep‐UV light‐emitting diode (LED). The smart ODR, composed of Al, Ni‐doped AlN (Ni:AlN) and p‐AlGaN, exhibits a high reflectivity of 94.2% at 280 nm and ohmic behavior with p‐Al0.6 Ga0.4 N, which allows simultaneous improvements in both externalquantum (8.49%) and wall‐plug (4.81%) efficiencies of the deep‐UV LED.