The main purpose of this study is focused on the defects within the layers of GaN over AlN thin films which were grown on the substrates of silicon (111) and LiAlO2 (100), respectively. The growth of three sapphire crystals is also addressed. During the epitaxial growth period, the Al pre-deposition time is very important for the defect on AlN/Si, and due to the high stacking fault energy, the partial dislocations in the AlN layers can not be observed. Cracks were found in the GaN films because of the great thermal mismatch between GaN itself and AlN which is up to 25%. Although the lattice mismatch between GaN and LiAlO2 is low, the thermal stress effect still could not be avoided. Cracks also occurred in the GaN films which were grown on LiAlO2 substrates.
For the sapphire pulled along [100] direction, the crystal has fewer amounts of bubbles at the lower rotation rate. For the sapphire pulled along [001] direction, the crystal with 4.5 mm/hr pulling rate has cracks along [001] direction, but the crystal with 4.0 mm/hr pulling rate has no cracks inside.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0620106-142052 |
| Date | 20 June 2006 |
| Creators | Lu, Chia-Ming |
| Contributors | Mitch Chou, none, none |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0620106-142052 |
| Rights | withheld, Copyright information available at source archive |
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