Study of Wurtzite InN epilayer and related defect analysis
| Autor: | Wang, Yan-Hsin, 王彥欣 |
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| Rok vydání: | 2010 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 98 The growth of InN thin films using plasma-assisted molecular beam epitaxy has been explored and the material properties of InN have been characterized by various technologies. Patterned substrates were designed to facilitate dislocation slipping and hence to reduce dislocation density. The study of the impact of the low temperature InN (LT-InN) buffer layers growth conditions on the quality of Wurtzite InN films revealed that, as evidenced by the reflection high-energy electron diffraction (RHEED) patterns, the growth mode changed from two dimensional to three dimensional when the thickness of LT-InN exceeded 20nm. With growth conditions remaining the same, increasing the growth rate of LT-InN improved film quality investigated by the full width at half maximum of rocking curve peaks, surface roughness measured by atomic force microscopy, threading dislocation estimated by X-ray diffraction (XRD), and photoluminescence spectrum. When growth temperature was raised from 440°C to 525°C, the full-width at half-maximum (FWHM) of (0002) rocking curve was reduced from 0.69°to 0.32°. Under optimized growth condition, the edge type dislocation density estimated by XRD rocking curve was close to that observed by plane-view TEM, 1.60×1010 cm-2. PL peaks at 15K and 300K were 0.666 and 0.655 eV, respectively. The relation between exciting power and PL integrated intensity confirmed that the observed PL signal was caused by band-to-band recombination. Circular notch micro-arrays were designed and fabricated to create free borders to allow dislocations to move to edges. Dislocations slipping to the edge of notches would disappear and stress would be released. The experiment was divided into two parts. First, notch patterns with hexagonal symmetry were produced on part of the Si(111) substrate prior to the growth of InN. X-ray diffraction studies indicated that the InN film grown on the patterned region showed lower dislocation density than that on the non-patterned region. Scanning electron microscopy images revealed larger grain size in the patterned region. Surface roughness measured by atomic force microscopy was 5.23nm in patterned area, which was better than that of 9.16nm in non-patterned region. The second part investigated the effect of post growth annealing on films grown on Si(111) substrate with and without AlN buffer layer. Array patterns were fabricated after InN growth and samples were annealed. The rocking curve peak width of the sample with AlN buffer layer was broadened while that of the sample without AlN buffer layer was improved after anneal. It is interpreted that the highly faulted AlN hindered the slipping of dislocations. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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