| Summary: | 碩士 === 國立彰化師範大學 === 光電科技研究所 === 98 === In this thesis, InN was grown on high quality GaN templates with inserting various thicknesses (0~60 nm) of low-growth-rate GaN (LG-GaN) buffers by molecular beam epitaxy (MBE). The crystal quality, microstructure variation and dislocation density of InN were analyzed by X-ray diffraction (XRD).
In chapter one, the characteristics of III-nitrides including crystal structure and defect types were first introduced. In chapter two, the operation theory of XRD and its related analysis technology applied in III-nitrides were reviewed. Finally, the detailed analysis of InN epi-films was discussed in chapter three
From analysis results, the twist angle of lattice variation for InN epilayer was 1.3°when InN was grown on GaN template directly, mainly because of difference in growth mechanism between MBE-grown epilayer and metal organic chemical vapor deposition (MOCVD)-grown GaN template. Moreover, no twist situation was found between InN and LG-GaN buffer if InN LG-GaN was grown on sapphire , due to same polarity of these two layers. It was found that the twist angle of InN can be greatly reduced by 0.9°with inserting an 10-nm LG-GaN buffer. However, the lattice variation was still worse than GaN template itself. Also, compared with the twist situation of InN directly grown on sapphire, the lattice variation of InN was effectively improved when InN was grown on GaN template with inserting an LG-GaN buffer.
Finally, the screw-type dislocation density and edge-type dislocation density for InN grown on MOCVD-grown GaN template with insertion of LG-GaN buffers were calculated to be 1~3×108 cm-2 and 1~2×1010 cm-2, respectively. However, the total dislocation density was only 20% of InN dislocation density if InN was grown on sapphire directly. The quality of InN should be further improved if lattice microstructure variation can be reduced by employing different growth condition of mechanism.
Finally, conclusion and future work of this thesis were given in chapter four.
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