title: Efficiency improvement of GaN-based ultraviolet light-emitting diodes with reactive plasma deposited AlN nucleation layer on patterned sapphire substrate.
abstract: The flip chip ultraviolet light-emitting diodes (FC UV-LEDs) with a wavelength of 365 nm are developed with the ex situ reactive plasma deposited (RPD) AlN nucleation layer on patterned sapphire substrate (PSS) by an atmospheric pressure metal-organic chemical vapor deposition (AP MOCVD). The ex situ RPD AlN nucleation layer can significantly reduce dislocation density and thus improve the crystal quality of the GaN epitaxial layers. Utilizing high-resolution X-ray diffraction, the full width at half maximum of the rocking curve shows that the crystalline quality of the epitaxial layer with the (RPD) AlN nucleation layer is better than that with the low-temperature GaN (LT-GaN) nucleation layer. The threading dislocation density (TDD) is estimated by transmission electron microscopy (TEM), which shows the reduction from 6.8 × 10(7) cm(-2) to 2.6 × 10(7) cm(-2). Furthermore, the light output power (LOP) of the LEDs with the RPD AlN nucleation layer has been improved up to 30 % at a forward current of 350 mA compared to that of the LEDs grown on PSS with conventional LT-GaN nucleation layer.
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsin-Chu 30010, Taiwan.
authors.forename: Chia-Yu
authors.initials: CY
authors.lastname: Lee
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsin-Chu 30010, Taiwan ; Department of Electrophysics, National Chiao Tung University, Hsin-Chu 30010, Taiwan.
authors.forename: An-Jye
authors.initials: AJ
authors.lastname: Tzou
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsin-Chu 30010, Taiwan.
authors.forename: Bing-Cheng
authors.initials: BC
authors.lastname: Lin
authors.affiliation: Microelectronic and Information System Research Center, National Chiao Tung University, Hsin-Chu 30010, Taiwan.
authors.forename: Yu-Pin
authors.initials: YP
authors.lastname: Lan
authors.affiliation: Advanced Optoelectronic Technology Incorporation, Hsinchu County 303, Taiwan.
authors.forename: Ching-Hsueh
authors.initials: CH
authors.lastname: Chiu
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsin-Chu 30010, Taiwan.
authors.forename: Gou-Chung
authors.initials: GC
authors.lastname: Chi
authors.affiliation: Optorun Co., Ltd., Saitama-ken 350-0801, Japan.
authors.forename: Chi-Hsiang
authors.initials: CH
authors.lastname: Chen
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsin-Chu 30010, Taiwan.
authors.forename: Hao-Chung
authors.initials: HC
authors.lastname: Kuo
authors.affiliation: Department of Electronic Engineering, Chang-Gung University, Taoyuan 333, Taiwan.
authors.forename: Ray-Ming
authors.initials: RM
authors.lastname: Lin
authors.affiliation: Department of Electrophysics, National Chiao Tung University, Hsin-Chu 30010, Taiwan ; Microelectronic and Information System Research Center, National Chiao Tung University, Hsin-Chu 30010, Taiwan.
authors.forename: Chun-Yen
authors.initials: CY
authors.lastname: Chang
keywords: Flip chip ultraviolet light-emitting diodes (FC UV-LEDs); GaN; Nucleation; Reactive plasma deposited AlN