Growth of semipolar GaN films on a-plane sapphire substrates with periodic line patterns

• Main Authors: Cheng, Wen-Hao, 鄭文豪
• Other Authors: Wu, Yew-Chung
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/81317639689335708861

碩士 === 國立交通大學 === 材料科學與工程學系 === 99 === As generally recognized, built-in electric field will emerge along the polar c-axis of GaN epitaxial layers when growing the GaN base LEDs on a-、c-plane sapphire substrates. This may cause distortions of energy band gap, thereby decreases the recombination probability of electron-hole pairs and affects the internal quantum efficiency of such a structure. Moreover, energy band gap distortions will also produce red-blue shift in the emission wavelength. In order to alleviate this built-in electric field, non-polar or semi-polar GaN should be grown on sapphire instead. In this thesis, a-plane line patterned sapphire substrates followed by growth of LED structure are fabricated and non-polar or semi-polar GaN is expected to grow on sapphire substrates. In the first experiment, the dry etching method is employed to produce both Pyramid-DPSS and Flat-DPSS with line patterns parallel to the flat of sapphire substrates. And the Flat-DPSS is observed to possess better properties in SEM surface morphology、FWHM of XRC and PL intensity…etc. However, it is examined to still be polar c-plane GaN under XRD θ-2θ scan. On the other hand, the semi-polar (10-11)GaN successfully grows on Pyramid-DPSS by its side walls. 　　In the second experiment, the a-plane line patterned sapphire substrates with 30° miscut to sapphire flat is fabricated. The semi-polar (10-11)GaN is successfully grown on specific (13-46)sapphire plane exposed by hybrid dry plus wet etching. And the wet etching method can repair the damaged surface caused by dry etching. Nevertheless, problems of growth rate and surface morphology still exist. The red-blue shift issues exist in LED devices manufacture may be resolved if these problems are overcome in the future research.