The properties of dilute bismuthides and rare-earth containing materials for applications in thermoelectrics, optoelectronics, and terahertz technology

Author(s)Dongmo, Pernell
Date Accessioned2016-02-11T13:32:46Z
Date Available2016-02-11T13:32:46Z
Publication Date2015
Abstract(In)GaAs compounds containing low concentrations of Bi are called dilute bismuthides. When Bi is incorporated, bandgap narrowing occurs because of valence band anticrossing (VBAC). The ability to tune the bandgap of this material is useful in the field of optoelectronics. Dilute bismuthides, or more specifically n-InGaBiAs, is also expected to be a good thermoelectric material because Bi is a heavy atom and the conduction band should be similar to InGaAs. A heavy Bi atom can effectively scatter heat phonons, which reduces the thermal conductivity. With similar conduction band to InGaAs, a relatively high thermoelectric power factor is expected as well. This dissertation discusses the electrical and thermoelectric properties of n-InGaBiAs. The dissertation also briefly discusses how this material is ideal for mid-infrared transparent contacts. Transparent contacts are useful for devices such as liquid crystal displays (LCDs) and solar cells. However, traditional transparent contact materials like indium tin oxide (ITO) only work at the visible to near-infrared range. At midinfrared wavelengths, indium tin oxide is highly reflective due its plasma frequency. Dilute bismuthides are potential candidates for mid-infrared transparent contacts because they are transparent in mid-infrared wavelengths and have relatively low sheet resistances. ErAs or TbAs nanoparticles can be embedded in GaAs or InGaAs by codeposition via molecular beam epitaxy (MBE). These materials have interesting properties that can be applied to thermoelectrics and terahertz technologies. For thermoelectrics, the nanoparticles have a dopant-like behavior and provide scattering centers for phonons. ErAs nanoparticles in GaAs provides the short carrier lifetimes and high dark resistance that is needed for a terahertz material. An interesting question one may ask is what will happen when both Er and Tb are co-deposited. It was hypothesized that core-shell nanoparticles would form through a strain-driven process when both Er and Tb are co-deposited. This dissertation discusses the observation of self-assembled rare-earth core-shell nanoparticles in InGaAs. The core-shell nanoparticles was observed using atom probe tomography (APT). The structure consisted of a mixed core (ErAs and TbAs) and a pure TbAs shell. A simple energetics model, which is also discussed in this dissertation, confirms the formation of core-shell nanoparticles. An application for InGaAs containing core-shell nanoparticles is terahertz technologies, or more specifically, a photoconductive switch. These nanoparticles are expected to provide the short carrier lifetimes and high dark resistance needed for THz applications using InGaAs, but more research needs to be performed. Unexpectedly, TbAs may appear to have a bandgap, rather than semimetal. A discussion about the band structure of TbAs is presented in this dissertation as well. Finally, this dissertation presents the future directions for these materials. For dilute bismuthides, materials with high Bi concentrations are ideal for mid-IR lasers, but growing these materials is not straightforward. This dissertation discusses some potential solutions to their growth and fabrication. For core-shell nanoparticles, more growths and characterization can be performed to determine how the rare-earth concentrations (or ratios) affect the number of core-shell nanoparticles. In conclusion, dilute bismuthides and (In)GaAs containing rare-earth, core-shell nanoparticles remain promising for applications in thermoelectrics, optoelectronics, and terahertz technologies.en_US
AdvisorZide, Joshua M. O.
DegreePh.D.
DepartmentUniversity of Delaware, Department of Materials Science and Engineering
DOIhttps://doi.org/10.58088/w6jk-r113
Unique Identifier938544020
URLhttp://udspace.udel.edu/handle/19716/17449
PublisherUniversity of Delawareen_US
URIhttp://search.proquest.com/docview/1727750820?accountid=10457
dc.subject.lcshBismuthides.
dc.subject.lcshIndium compounds.
dc.subject.lcshGallium compounds.
dc.subject.lcshArsenic compounds.
dc.subject.lcshNanoparticles.
dc.subject.lcshThermoelectricity.
dc.subject.lcshOptoelectronics.
dc.subject.lcshTerahertz technology.
TitleThe properties of dilute bismuthides and rare-earth containing materials for applications in thermoelectrics, optoelectronics, and terahertz technologyen_US
TypeThesisen_US
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