Initial stages of the ion-beam assisted epitaxial GaN film growth on 6H-SiC(0001)

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• 作者：L. Neumann^a ; J.W. Gerlach^a ; ^{juergen.gerlach@iom-leipzig.de} ; B. Rauschenbach^a ; ^b
• 关键词：Ion-beam assisted epitaxy ; Gallium nitride ; High-energy electron diffraction ; Scanning tunneling microscope ; Growth mode ; Ultra-thin films
• 刊名：Thin Solid Films
• 出版年：2012
• 期刊代码：78_00406090
• 类别：ph
• 出版时间：30 March, 2012
• 卷：520
• 期：11
• 页码：3936-3945
• 文件大小：1888 K

摘要

Ultra-thin gallium nitride (GaN) films were deposited using the ion-beam assisted molecular-beam epitaxy technique. The influence of the nitrogen ion to gallium atom flux ratio (I/A ratio) during the early stages of GaN nucleation and thin film growth directly, without a buffer layer on super-polished 6H-SiC(0001) substrates was studied. The deposition process was performed at a constant substrate temperature of 700 掳C by evaporation of Ga and irradiation with hyperthermal nitrogen ions from a constricted glow-discharge ion source. The hyperthermal nitrogen ion flux was kept constant and the kinetic energy of the ions did not exceed 25 eV. The selection of different I/A ratios in the range from 0.8 to 3.2 was done by varying the Ga deposition rate between 5 脳 10¹³ and 2 脳 10¹⁴ at. cm^鈭?#xA0;2 s^鈭?#xA0;1. The crystalline surface structure during the GaN growth was monitored in situ by reflection high-energy electron diffraction. The surface topography of the films as well as the morphology of separated GaN islands on the substrate surface was examined after film growth using a scanning tunneling microscope without interruption of ultra-high vacuum. The results show, that the I/A ratio has a major impact on the properties of the resulting ultra-thin GaN films. The growth mode, the surface roughness, the degree of GaN coverage of the substrate and the polytype mixture depend notably on the I/A ratio.