Defense Date


Document Type


Degree Name

Master of Science



First Advisor

Dr. Alison Baski


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.


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Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

June 2008

Included in

Physics Commons