Structure and Defect of GaN Studied by Transmission Electron Microscopy

• Main Authors: Lin, Chieh Hsiu, 林睫修
• Other Authors: Feng Ming-Shiann
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/90391915710489768495

碩士 === 國立交通大學 === 材料科學與工程研究所 === 85 === In this thesis, we have studied the structure and defect of GaN films grown on (0001)sapphire by transmission electron microscope (TEM). We have grown low temperature (525 C) GaN buffer layer on (0001) sapphire substrate then grown GaN film at high temperature (1025 C) by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). In our LP-MOCVD system, we used different MO source, triethylgallium (TEGa) and trimethylgallium (TMGa) to grow GaN films. We compare the diffraction patterns and TEM images of GaN films grown by two MO source to indicate the buffer layer structure,the lattice parameters of GaN films, lattice misfit between GaN and sapphire,and dislocations of GaN films. Two types structure of LT-GaN buffer layers are formed by two types MO source during GaN epitaxial growth. One is columnar structure from TMGa source and the other is stacked like disc stacked together from TEGa source. Lattice misfits of GaN/ sapphire interface based on (1 0 -1 0)GaN // (2 -1 -1 0)Sapphire and (2 -1 -1 0)GaN // (3 -3 0 0)Sapphire are about 16.1%.The lattice parameters a & c of GaN films of initial layers are smaller than those of layers close to the surface (final stage). From TEM images, the dislocation density of GaN films by TEGa source is less than that by TMGa source. The growth rate of GaN is slower which results in better crystallization and less defect density.