This thesis uses the techniques of atomic force microscope (AFM) and conductive AFM (C-AFM) to study the conduction properties of n-type GaN films. A total of 16 samples were examined and grouped according to their surface morphologies and conduction behaviors. The most common type of surface morpliology was that of Ga-rich samples having undulating "hillocks" with interspersed holes. Although most of the samples had this common morphology, their local conduction behaviors were not all similar. Local I-V spectra of the tip-sample Schottky contact could be grouped according to three major types: low leakage, high leakage, and "p-type". The highest quality samples with low leakage were usually grown at moderate temperatures (~650°C). For such samples, localized leakage only occurred at screw dislocations located at small pits terminating surface hillocks. I-V spectra taken on and off such hillocks were fit in forward bias to determine whether field emission or Frenkel-Poole conduction were dominant. Although field emission is a good fit compared to Frenkel-Poole, yielding reasonable values for the barrier height, the results are not yet conclusive without variable temperature studies.
Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd-2245 |
Date | 01 January 2005 |
Creators | Cooper, Katherine |
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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