Characterization of hexagonal Boron Nitride and rhombohedral Boron Nitride

• Main Authors: YuCheng, Chen, 陳宥錚
• Other Authors: Kun-Yu Lai
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/t8qmz3

碩士 === 國立中央大學 === 光電科學與工程學系 === 107 === Hexagonal Boron Nitride (h-BN) with sp2 bonding is an attractive p-type material for the application in deep-ultraviolet light emitting diodes (DUV LEDs). This is due to the wide bandgap (~ 6.0 eV) and low activation energy of acceptors (~30 meV) of h-BN, rendering high transmission of DUV photons and high p-type conductivity for DUV LEDs. However, rhombohedral BN (r-BN), also with sp2 bonding, is of a similar lattice structure with h-BN, which yields almost identical X-ray diffraction (XRD) angles. With the diffraction-peak difference less than 0.1°, h-BN and r-BN can not be differentiated by XRD patterns alone, but requires high-resolution transmission electron microscope (HRTEM) to reveal the minor difference in lattice between h-BN and r-BN. In this study, we perform epitaxial growth of BN by metal-organic chemical vapor deposition (MOCVD) on single-crystalline aluminum nitride (AlN), which is previously grown on the sapphire substrate. In order to improve the crystal qualities of BN, V/III ratios (i.e. the molar-flow ratio of NH3 to triethylborane) was varied from 237 to 2454. According to the characterization results with XRD and HRTEM, the MOCVD-grown BN wafer contains hexagonal and rhombohedral lattices at the BN/AlN interface, and the wafer grown with the V/III ratio of 663 exhibit superior qualities to those attained with the ratios of 237 and 2454.