Open AccessIs a thin p-GaN layer possible for making high-efficiency AlGaN-based deep-ultraviolet light-emitting diodes?
Author(s) -
Weidong Wang,
Chunshuang Chu,
Jiamang Che,
Sheng Hang,
Hua Shao,
Kangkai Tian,
Yonghui Zhang,
Zihui Zhang
Publication year - 2021
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.434636
Subject(s) - quantum efficiency , materials science , optoelectronics , light emitting diode , current crowding , layer (electronics) , diode , ultraviolet , thin film , wide bandgap semiconductor , indium gallium nitride , optics , current (fluid) , gallium nitride , nanotechnology , physics , thermodynamics
In this report, we investigate the impact of a thin p-GaN layer on the efficiency for AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs). According to our results, the light extraction efficiency (LEE) becomes higher with the decrease of the p-GaN layer thickness, which can be ascribed to the decreased absorption of DUV emission by the thin p-GaN layer. Moreover, we also find that the variation trend of external quantum efficiency (EQE) is consistent with that of LEE. Therefore, we can speculate that high-efficiency DUV LEDs can be achieved by using thin p-GaN layer to increase the LEE. However, a thin p-GaN layer can also cause severe current crowding effect and the internal quantum efficiency (IQE) will be correspondingly reduced, which will restrict the improvement of EQE. In this work, we find that the adoption of a current spreading layer for such DUV LED with very thin p-GaN layer can facilitate the current spreading effect. For the purpose of demonstration, we then utilize a well-known p-AlGaN/n-AlGaN/p-AlGaN (PNP-AlGaN) structured current spreading layer. Our experimental and numerical results show that, as long as the current crowding effect can be suppressed, the DUV LED with thin p-GaN layer can significantly increase the EQE and the optical power thanks to the enhanced LEE.