This thesis uses the techniques of atomic force microscopy (AFM) and conductiveAFM (CAFM) to study defect sites on GaN films. In particular, these defect sites demonstrate current leakage under reverse-bias conditions that are detrimental to device fabrication. Two growth techniques that were used to improve this leakage behavior for samples in this study included: epitaxial lateral overgrowth (ELO) and nano-ELO using a Si3N4 film. Both techniques decrease defects such as threading dislocations by controlling the nucleation and growth behavior of the GaN films. The EL0 technique uses a patterned dielectric film to laterally grow micron-wide regions (referred to as 'wings') that minimize dislocation defects. Our CAFM studies indicate that ELO films have no detectable leakage sites in these wing regions; however, between these regions the films have typical leakage site densities seen for standard films on the order of 107cm-3. The nano-ELO technique utilizes a porous Si3N4 film to reduce defects over the entire film, and CAFM data indicate nearly a factor of ten reduction in leakage site densities. The nano-ELO technique is therefore optimal for an overall improvement in film quality, whereas the ELO technique is suitable for device fabrication in patterned regions with optimized film quality.
| Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd-2411 |
| Date | 01 January 2007 |
| Creators | Kasliwal, Vishal P. |
| Publisher | VCU Scholars Compass |
| Source Sets | Virginia Commonwealth University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | © The Author |
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