Dissertation
OPTICAL PHENOMENA IN OXIDE SEMICONDUCTORS
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004604
Handle:
https://hdl.handle.net/2376/118801
Abstract
Acceptor doping of β-Ga2O3 has been driven by its potential as a semi-insulating materialto serve as a substrate high-voltage/high-power devices. Strengthening this use-case is the ability to grow large, high-quality single crystals quickly and inexpensively. In this work, infrared and UV/Visible spectroscopy measurements were performed on β-Ga2O3 doped with zinc or copper. β-Ga2O3:Zn had significant hydrogen incorporation in the as- grown state, with a corresponding O-H mode in the infrared at 3486.7 cm-1. This assignment was confirmed by annealing in deuterium and observing the corresponding O-D mode at 2582.9 cm-1. A prominent peak at 5147.6 cm-1 has been attributed to an Ir4+ electronic transition and the sideband field implies the existence of tetrahedrally- coordinated zinc. Oxygen annealing increased the electrical resistance to more than 1 TΩ. β-Ga2O3:Cu exhibited room-temperature persistent photochromism upon exposure to sub-bandgap light. The photochromism was accompanied by the appearance of O-H modes in the infrared and a decrease in the Ir4+ peak intensity. It is proposed that light of sufficient energy releases the hydrogen from CuGa-HO complexes, which then forms the O-H bonds that were observed.
When annealed under a flowing gas atmosphere of hydrogen and humid argon, single crystals of BaTiO3 exhibit persistent photoconductivity (PPC) at room temperature upon exposure to sub-bandgap light. The PPC is characterized by a broad infrared absorption peak at 5000 cm-1 and is accompanied by a factor of two decrease in electrical resistance. Larger gas flows were observed to correspond with larger infrared absorption. The photon energy threshold for PPC is similar to that observed in SrTiO3 at 2.9 eV. Due to the similarities in behavior to PPC in SrTiO3, an analogous model for the case of BaTiO3 is proposed.
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Details
- Title
- OPTICAL PHENOMENA IN OXIDE SEMICONDUCTORS
- Creators
- Christopher Paul Pansegrau
- Contributors
- Matthew D McCluskey (Advisor)Yi Gu (Committee Member)Gary S Collins (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Physics and Astronomy, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 167
- Identifiers
- OCLC#: 1365398865; 99900901029901842
- Language
- English
- Resource Type
- Dissertation