The Doping And Characterization Of Erbium In Gallium Nitride

Author : Xingmin Cai
Publisher : Open Dissertation Press
ISBN 13 : 9781361238172
Total Pages : pages
Book Rating : 4.2/5 (381 download)

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Download or read book Growth, Doping and Nanostructures of Gallium Nitride written by Xingmin Cai and published by Open Dissertation Press. This book was released on 2017-01-26 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Growth, Doping and Nanostructures of Gallium Nitride" by Xingmin, Cai, 蔡興民, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled GROWTH, DOPING AND NANOSTRUCTURES OF GALLIUM NITRIDE Submitted by Cai Xing Min for the degree of Doctor of Philosophy at The University of Hong Kong in September 2005 Due to its exceptional properties, such as the direct and wide band gap and high thermal stability, gallium nitride (GaN) is widely used in optoelectronics and high temperature/high power devices. Moreover, GaN has great potential for spintronic and nanoelectronic applications. Hence research on the nanostructures and doping of GaN has become intensive in recent years. Theoretical calculations predict that Mn doped GaN has Curie temperatures above room temperature. However, experimental results have not been consistent and a wide range of magnetic properties was reported for GaN: Mn. In this work, doping by thermal diffusion and doping during molecular beam epitaxy (MBE) growth were investigated. It was found that GaN wafers doped with Mn and Cr by thermal diffusion were ferromagnetic at 300 K, while for the MBE grown GaMnN samples, ferromagnetism up to 56 K was observed. This illustrates the importance of the material quality and the doping mechanism on the magnetic properties of the sample. One possible way to achieve improved material quality of GaN is to fabricate nanowires instead of thin films. Due to the lack of lattice matched substrates for GaN, it is difficult to grow epitaxial layers with low concentration of defects. On the other hand, GaN nanowires with good crystalline quality could be grown on a wider range of substrates. Therefore, systematic investigation of GaN nanowire growth has been performed. The effects of catalyst, temperature, and Ga to N ratio on the obtained morphology of GaN were studied. It was found that metallic Ni and Au were suitable catalysts for GaN nanowire growth, while nickel nitrate resulted in the growth of SiO nanowire bunches. The effect of the Ga/N ratio on the morphology of GaN nanowires was studied in detail for Ni catalyzed growth. It was found that the morphology of GaN nanowires strongly depended on the Ga/N ratio. In relatively Ga rich condition, smooth-surfaced GaN nanowires grew along [1010], while in relatively N rich condition, a mixture of smooth-surfaced and stacked-cone GaN nanowires growing along [0001] was obtained. In addition, in the N rich condition, lateral growth of GaN nanowires and a completely new morphology were observed. The growth mechanisms responsible for the different morphologies were discussed. In addition, growth of InN and In Ga N nanostructures was also studied. x 1-x Different catalysts were tested for growing InN nanowires, and successful fabrication of nanowires was achieved for Au and Ag. Both hexagonal and cubic InN nanorods with polyhedral ends were obtained and their formation mechanism was discussed. In Ga N nanowires with a core/shell structure were successfully fabricated. Free x 1-x standing In Ga N nanocoils and In Ga N nanowires coiled around one another x 1-x x 1-x were observed with longer growth time and on substrates with thicker gold layers. DOI: 10.5353/th_b3580639 Subjects: Semiconductor doping Nanostructures Gallium nitride