Optical properties of electrochemical etched GaN epitaxial structures

• Main Authors: Guo-Yi Shiu, 許國翊
• Other Authors: Chia-Feng Lin
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/62386293334917130934

碩士 === 國立中興大學 === 材料科學與工程學系所 === 104 === In this thesis, we investigated the nonporous Distributed Bragg Reflector(DBR) which was fabricated by electrochemical wet etching (EC)process, and applied to InGaN-based light emitting diode (LED)for optical properties discussion. Before the epitaxial of InGaN –based LED, twelve pairs period structure consisted of high doping and low doping concentration GaN film were growth on the u-GaN layer. Using Nd:YVO4355nm laser scribing system and electrochemical wet etching process, the heavy doping concentration GaN layer would be transformed into low refractive index nano-porous structure.The DBR structure with low refractive index material stacked high refractive index material was form after these process. An InGaN light emitting diode embed nonporous DBR structure was fabricated. In this DBR structure, it consisted of 1/4λoptical thickness nonporous GaN and undoped GaN .The central wavelength of the nonporous DBR structure was located at 442.3nm with 57nm linewidth, and best reflectivity located at 454.2nm with a 99.1% peak reflectivity. Both of EL and PL spectra, the light extraction efficiency was enhance caused by embed nonporous DBR .By using angle-resoved PL spectra, we found the penetration depth of nanoporous DBR which was about 278nm. Non-linear emission intensity and linewidth reducing effect, from 11.8nm to 0.73nm, were observed by increasing Nd:YVO4 355nm laser pumping power. The structure had potential for developing high Quality factor vertical cavity surface emitting laser (VCSELs).