Transmission Electron Microscopy Studies of GaN-based and ZnO-based Films
Date Issued
2007
Date
2007
Author(s)
Liu, Ta-Chung
DOI
en-US
Abstract
In the field of optoelectronic materials, the applications of GaN have gotten more and more mature recently. In this study, we focused on the observations for lattice quality of the non-polar GaN in the first part of experimental work. Due to the property of large mismatch anisotropy, the problem of low lattice epitaxy quality usually exists, so that we have to resolve it. Hence, we deposited 7.5nm and 15nm LT-AlN as buffer layers on two samples, trying to make improvement on lattice quality. Via observations of TEM, we can find that thicker buffer layer reduced threading dislocations obviously, and got better lattice quality. In the other hand, from the microstructural analyses of TEM, we observed a lot of stacking-faults, and confirmed that most of the threading dislocations are pure-screw dislocations.
Nevertheless, ZnO have some physical properties which make it have more prospective development than GaN. ZnO is quite hot in the field of light-emitting materials in recent years. We focused on the observation of three ZnO samples with different growth conditions in the second half content. The first sample is ZnO nano-dots embedded, and the result is very satisfying. Furthermore, the last two samples are compared as ZnO deposited on different substrates. HR-TEM, XRD spectrum, and PL…etc. are the means we use for studying this samples. It is obvious that ZnO is polycrystalline when grown on silicon, and the density of dislocations and stacking-faults are much higher than the one on sapphire. To conclude, sapphire is better substrate for ZnO film epitaxy.
Subjects
氮化鎵
氧化鋅
薄膜
穿透式電子顯
Transmission Electron Microscopy
GaN
ZnO
Film
observation
Type
thesis
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