Fabrication of Nitride-based Template and Epitaxial Growth of Nitride-related Material

• Main Authors: Chang, Li-Chuan, 張力權
• Other Authors: Kuo, Cheng-Huang
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/84f3rv

博士 === 國立交通大學 === 照明與能源光電博士學位學程 === 102 === In this dissertation, the fabrication of GaN nanorod template, the growth mechanism and characterization of GaN epitaxial layer grown on GaN nano rod template, and the characteristics of GaN-based LEDs prepared on GaN nano rod template have been studied. The improvement of current spreading in GaN-based LEDs with high quality Si-doped n-GaN prepared on GaN nanorod template is investigated. The mechanism and characterization of GaN grown on high aspect ratio patterned sapphire substrate (HARPSS) with physical vapor deposition (PVD) AlN nucleation layer and characteristics of GaN-based LEDs have been also studied. In addition, we also discuss the growth and characteristics of AlGaN grown on nano patterned sapphire substrate (NPSS) with PVD AlN nucleation layer. The primary results obtained in this dissertation are summarized as follow: (a) The uniform and high density GaN nano rods were fabricated by Ni nano mask. The diameter and density of GaN nano rods were around 250 nm~500 nm and 3 × 108 cm-2. In this dissertation, the GaN nano rod templates for epitaxial growth were fabricated by Ni mask. It was found that GaN epitaxial layer could directly grow on GaN nanorod template without buffer layer. It was also found that the GaN grown on GaN nanorod template showed narrower FWHM of GaN (102) in DCXRD (~370 sec), as compared with conventional GaN without GaN nanorod template. It was found that we can enhance LED output power by GaN nanorod template due to both increases internal quantum efficiency and light extraction efficiency, as compared with conventional LED. With 20 mA injection, the LED output power was enhanced by 29.8%, as compared with conventional LEDs. (b) For current spreading improvement in GaN-based LEDs, the GaN-based LED with high quality heavily Si-doped n-GaN prepared on GaN nanorod template was proposed and fabricated. It was found that we can reduce etching pits density in heavily Si-doped n-GaN epitaxial layer by using the GaN nanorod template (~3.9 × 108 cm-2), as compared to the conventional heavily Si-doped n-GaN without GaN nanorod template. It was found that we can enhance 14.8% LED light output power by improving current spreading with high quality heavily Si-doped n-GaN prepared on GaN nanorod template. (c) The high-quality GaN epitaxial layer grown on HARPSS with PVD AlN nucleation layer by metal organic chemical vapor deposition (MOCVD) have been studied. The growth mechanism and characterization of GaN epitaxial layer grown on HARPSS with different AlN nucleation layers have been studied. It was found that the GaN prepared on HARPSS with PVD AlN nucleation layer showed lower TDs and pure wurzite structure in TEM, as compared with GaN prepared on HARPSS with MOCVD grown AlN nucleation layer. The LEDs prepared on HARPSS with PVD AlN nucleation layer could enhance the 46% LED light output power, as compared with LED prepared on HARPSS with MOCVD grown AlN nucleation layer. (d) The AlGaN epitaxial layer prepared on nano patterned sapphire substrate with PVD AlN nucleation layer was proposed and fabricated. It was found that the AlGaN grown on NPSS with PVD AlN nucleation layer showed narrower FWHM of AlGaN(102) in DCXRD (~631sec), as compared with AlGaN prepared on planar sapphire substrate and PVD AlN nucleation layer. In addition, the formation of two peak phenomenon found in PL measurement for AlGaN prepare on NPSS was also discussed.