Growth and Luminescence Properties of Core-Shell InGaN/GaN Nano-Facets Multi-Qunatum Wells (MQWs) on GaN Nanorods

• Main Authors: Li, Yun-Jing, 李昀瑾
• Other Authors: Chang, Chun-Yen
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/68044221138278685710

碩士 === 國立交通大學 === 照明與能源光電研究所 === 99 === Recently, one-dimensional structures are attracting much interest in the reduction of dislocations, the promotion of light extraction efficiency and the enlarged active area. In this thesis, we demonstrate the phosphor-free nanorods with core-shell structure have the polychromatic emission with color temperature about 6,000 K (a natural white light). A core-shell nanorod includes a shell of InGaN/GaN multi-quantum wells (MQWs) and a core of GaN nanorod. The fabrication procedure as follows: The nanorods arrays arrange in a 12-fold symmetric photonic quasicrystal (PQC) pattern on c-plane GaN template were fabricated by nano-imprint lithography, and followed by the regrowth of MQWs on the crystalline facets of nanorods. After regrowth, each core-shell nanorod with arrow shape is composed of nonpolar {"10" "1" ̅"0" } facets on sidewalls and semipolar {"10" "1" ̅"1" } facets on a pyramidal top. Accordingly, the polarization effects can also be suppressed by growing semipolar and nonpolar planes of nanorods. The core-shell nanorod with an inhomogeneous indium content distribution could be realized by two mechanisms: One is the mass transport model, including the different surface diffusion constants cause the different indium incorporation efficiency on semipolar and nonpolar planes. In the other hand, the gradient indium distribution on each facet is influenced by the gas phase diffusion. The other one is the surface modification model, including the lower chemical potential at the intersection of growth planes, and strain relaxed by the new-born facets. Therefore, whole core-shell nanorod has the obvious difference of indium incorporation efficiency distribute from the bottom to top portion of nanorods. In addition, a higher indium content of nanorods was also attained by lowering the regrowth temperature, whereas the degraded sidewalls of core-shell nanorods were caused by the lower species mobility. As a result, the polychromatic emission will be formed and the color temperature value can be tuned by the different regrowth parameters of MQWs nano-facets on nanorods. A phosphor-free white light emission is achieved by the core-shell nanorods technology. Worth a mention was that the random lasing action was achieved by nanorods arranged in a12-fold PQC pattern.