UV-C Light Emitting Diodes with Porous n-AlGaN Light Scattering Structure

• Main Authors: Bo-Syun Hong, 洪伯勳
• Other Authors: 林佳鋒
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/fz8h37

碩士 === 國立中興大學 === 材料科學與工程學系所 === 106 === The porous AlGaN UV-C LED with high Al content used to enhance the UV-C light extraction efficiency (LEE) was demonstrated in this study. P-type GaN doped with Mg in order to increase the hole carries results in the absorption of UV-C cause the low LEE in UV-C devices. Flip chip process always apply to UV-C LED because of the backward light extraction through the n-AlGaN. By the pre-doped Si and selective electrochemical wet etching process, the n-AlGaN was transfer from bulk to porous structure. With the 213 nm laser stimulated, the PL center wavelength shift from 272.75 nm to 274.82 nm, FWHM narrow from 8.02 nm to 10.14 nm. By measuring the power of the 213 nm laser reflected by the sample, the 213 nm laser would be absorbed and caused the lower PL intensity by the porous. In the power dependent PL measurement, similar peak wavelength and FWHM (shift less than 1 nm) was observed in high power density (0.2~1.42 W/cm2). Porous structure UV-C LED enhanced the EL intensity about 24%, with the center wavelength shift from 286.53 nm to 286.82 nm and the FWHM narrow from 10.15 nm to 9.96 nm. The IQE (80 K) of non-treated and porous structure UV-C LED was calculated 15.9% and 32.6%, respectively. In the measurement of far field radiation patter with alpha-BBO Glan-laser polarizer, the porous structure increases the light extraction of TE mode in normal direction and TM mode in all direction. The porous structure in UV-C LED enhanced the light extraction efficiency without large difference in peak wavelength and FWHM. Porous structure AlGaN UV-C LED increased the light extraction contribution of TM mode in normal direction.