Abstract
We report deep ultraviolet (UVC) emitting core-shell-type AlGaN/AlN multiple quantum wells (MQWs) on the AlN nanorods which are prepared by catalyst/lithography free process. The MQWs are grown on AlN nanorods on a sapphire substrate by polarity-selective epitaxy and etching (PSEE) using high-temperature metal organic chemical vapor deposition. The AlN nanorods prepared through PSEE have a low dislocation density because edge dislocations are bent toward neighboring N-polar AlN domains. The core–shell-type MQWs grown on AlN nanorods have three crystallographic orientations, and the final shape of the grown structure is explained by a ball-and-stick model. The photoluminescence (PL) intensity of MQWs grown on AlN nanorods is approximately 40 times higher than that of MQWs simultaneously grown on a planar structure. This result can be explained by increased internal quantum efficiency, large active volume, and increase in light extraction efficiency based on the examination in this study. Among those effects, the increase of active volume on AlN nanorods is considered to be the main reason for the enhancement of the PL intensity.
Highlights
The mixed-polarity AlN template was grown by a bottom-up approach, and the AlN nanorods were fabricated by top-down wet chemical etching
We realized a lithography-free approach to fabrication of AlN nanorods that combines bottom-up growth of a mixed-polarity AlN template using metal–organic chemical vapor deposition (MOCVD) and top-down wet chemical etching by polarity-selective epitaxy and etching (PSEE)
It was confirmed that a mixed-polar AlN template could be grown by controlling only the annealing temperature before growth process
Summary
We report deep ultraviolet (UVC) emitting core-shell-type AlGaN/AlN multiple quantum wells (MQWs) on the AlN nanorods which are prepared by catalyst/lithography free process. The photoluminescence (PL) intensity of MQWs grown on AlN nanorods is approximately 40 times higher than that of MQWs simultaneously grown on a planar structure. This result can be explained by increased internal quantum efficiency, large active volume, and increase in light extraction efficiency based on the examination in this study. Core-shell-type UVC emitting MQWs grown on AlN nanorods which is formed on sapphire substrate is reported for the first time. Lower growth temperature compared to our previous study provided high density AlN nanorods with better reproducibility
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