title: Enhanced output power of GaN-based LEDs with embedded AlGaN pyramidal shells.
abstract: In this article, the characteristics of GaN-based LEDs grown on Ar-implanted GaN templates to form inverted Al0.27Ga0.83N pyramidal shells beneath an active layer were investigated. GaN-based epitaxial layers grown on the selective Ar-implanted regions had lower growth rates compared with those grown on the implantation-free regions. This resulted in selective growth, and formation of V-shaped concaves in the epitaxial layers. Accordingly, the inverted Al0.27Ga0.83N pyramidal shells were formed after the Al0.27Ga0.83N and GaN layers were subsequently grown on the V-shaped concaves. The experimental results indicate that the light-output power of LEDs with inverted AlGaN pyramidal shells was higher than those of conventional LEDs. With a 20 mA current injection, the output power was enhanced by 10% when the LEDs were embedded with inverted Al0.27Ga0.83N pyramidal shells. The enhancement in output power was primarily due to the light scattering at the Al0.27Ga0.83N/GaN interface, which leads to a higher escape probability for the photons, that is, light-extraction efficiency. Based on the ray tracing simulation, the output power of LEDs grown on Ar-implanted GaN templates can be enhanced by over 20% compared with the LEDs without the embedded AlGaN pyramidal shells, if the AlGaN layers were replaced by Al0.5Ga0.5N layers.
authors.affiliation: Institute of Electro-Optical Science and Engineering, National Cheng Kung University, Tainan City 70101, Taiwan.
authors.forename: Shang-Ju
authors.initials: SJ
authors.lastname: Tu
authors.forename: Jinn-Kong
authors.initials: JK
authors.lastname: Sheu
authors.forename: Ming-Lun
authors.initials: ML
authors.lastname: Lee
authors.forename: Chih-Ciao
authors.initials: CC
authors.lastname: Yang
authors.forename: Kuo-Hua
authors.initials: KH
authors.lastname: Chang
authors.forename: Yu-Hsiang
authors.initials: YH
authors.lastname: Yeh
authors.forename: Feng-Wen
authors.initials: FW
authors.lastname: Huang
authors.forename: Wei-Chih
authors.initials: WC
authors.lastname: Lai
mesh_terms: D017607:Aluminum Compounds / Q000737:chemistry*; D000537:Aluminum Oxide / Q000737:chemistry; D001128:Argon / Q000737:chemistry; D011211:Electric Power Supplies; D004581:Electronics; D005708:Gallium / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D055096:Optical Devices; D045663:Quantum Dots
chemical_list: D017607:Aluminum Compounds; C513700:aluminum gallium nitride; C473348:gallium nitride; D001128:Argon; D005708:Gallium; D000537:Aluminum Oxide