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Photo-Induced Electron Paramagnetic ...

Willoughby, William Ryan.

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Photo-Induced Electron Paramagnetic Resonance Study of Charge Transfer in Compensated Gallium Nitride Substrates Grown by the High Nitrogen Pressure Solution Method.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Photo-Induced Electron Paramagnetic Resonance Study of Charge Transfer in Compensated Gallium Nitride Substrates Grown by the High Nitrogen Pressure Solution Method./
作者:	Willoughby, William Ryan.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2019,
面頁冊數:	127 p.
附註:	Source: Dissertations Abstracts International, Volume: 80-11, Section: B.
Contained By:	Dissertations Abstracts International80-11B.
標題:	Applied physics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=13426712
ISBN:	9781392149133

Photo-Induced Electron Paramagnetic Resonance Study of Charge Transfer in Compensated Gallium Nitride Substrates Grown by the High Nitrogen Pressure Solution Method.
Willoughby, William Ryan.

Photo-Induced Electron Paramagnetic Resonance Study of Charge Transfer in Compensated Gallium Nitride Substrates Grown by the High Nitrogen Pressure Solution Method. - Ann Arbor : ProQuest Dissertations & Theses, 2019 - 127 p.

Source: Dissertations Abstracts International, Volume: 80-11, Section: B.

Thesis (Ph.D.)--The University of Alabama at Birmingham, 2019.

This item must not be sold to any third party vendors.

Charge transfer occurring in semi-insulating GaN crystals grown by the high nitrogen pressure solution (HNPS) method was investigated using electron paramagnetic resonance (EPR) spectroscopy. Samples were semi-insulating due to compensation of residual shallow oxygen donors with Mg and/or Be acceptor impurities. EPR was detected after illumination with photon energies greater than 2.7 eV in samples containing at least 1017 cm-3 beryllium atoms. The resonance consisted of two Gaussian lines. One was stable at temperatures less than 25 K with isotropic g=1.989 and was attributed to a paramagnetic neutral acceptor state. This resonance was quenched with photon energies between 0.5 eV and 2.7 eV, and warming the sample to temperatures greater than 50 K also decreased the EPR intensity. The other resonance with g = 1.945, g = 1,941 was only detected while the sample was under high intensity illumination and was attributed to a paramagnetic state associated with neutral shallow O donors.EPR photo-excitation (A- + hν → A0 + e-) and photo-quenching (A0 + hν → A- + h+) processes were systematically observed by monitoring the intensity of the g=1.989 resonance during and after sample illumination with various photon energies in the range 0.5 eV ≤ hν ≤ 3.2 eV . The intensity of this resonance was proportional to the concentration of neutral acceptors, allowing charge transfer rates to be directly observed with EPR.Charge transfer was modeled with a set of rate equations that tracked neutral acceptor, neutral donor, and charge carrier concentrations. Optical cross sections were extracted from best fits that used a pattern search algorithm for parameter optimization. The cross sections were analyzed using an expression for absorption by defects with strong electron-phonon coupling. The zero-phonon line for photo-excitation and photo-quenching was 2.5 eV and 0.80 eV, respectively, in good agreement with predictions for CN. Thermal quenching of CN-related EPR can only be explained by electron emission from a beryllium-related trap level close to the conduction band.The analysis shows that unintentional carbon impurities in semi-insulating HNPS GaN substrates play a key role in charge transfer as CN, and the work presents a significant advancement in the interpretation of time-dependent photo-EPR measurements.

ISBN: 9781392149133Subjects--Topical Terms:

3343996
Applied physics.
Subjects--Index Terms:

EPR

Photo-Induced Electron Paramagnetic Resonance Study of Charge Transfer in Compensated Gallium Nitride Substrates Grown by the High Nitrogen Pressure Solution Method.
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500 $a Source: Dissertations Abstracts International, Volume: 80-11, Section: B.
500 $a Publisher info.: Dissertation/Thesis.
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520 $a Charge transfer occurring in semi-insulating GaN crystals grown by the high nitrogen pressure solution (HNPS) method was investigated using electron paramagnetic resonance (EPR) spectroscopy. Samples were semi-insulating due to compensation of residual shallow oxygen donors with Mg and/or Be acceptor impurities. EPR was detected after illumination with photon energies greater than 2.7 eV in samples containing at least 1017 cm-3 beryllium atoms. The resonance consisted of two Gaussian lines. One was stable at temperatures less than 25 K with isotropic g=1.989 and was attributed to a paramagnetic neutral acceptor state. This resonance was quenched with photon energies between 0.5 eV and 2.7 eV, and warming the sample to temperatures greater than 50 K also decreased the EPR intensity. The other resonance with g = 1.945, g = 1,941 was only detected while the sample was under high intensity illumination and was attributed to a paramagnetic state associated with neutral shallow O donors.EPR photo-excitation (A- + hν → A0 + e-) and photo-quenching (A0 + hν → A- + h+) processes were systematically observed by monitoring the intensity of the g=1.989 resonance during and after sample illumination with various photon energies in the range 0.5 eV ≤ hν ≤ 3.2 eV . The intensity of this resonance was proportional to the concentration of neutral acceptors, allowing charge transfer rates to be directly observed with EPR.Charge transfer was modeled with a set of rate equations that tracked neutral acceptor, neutral donor, and charge carrier concentrations. Optical cross sections were extracted from best fits that used a pattern search algorithm for parameter optimization. The cross sections were analyzed using an expression for absorption by defects with strong electron-phonon coupling. The zero-phonon line for photo-excitation and photo-quenching was 2.5 eV and 0.80 eV, respectively, in good agreement with predictions for CN. Thermal quenching of CN-related EPR can only be explained by electron emission from a beryllium-related trap level close to the conduction band.The analysis shows that unintentional carbon impurities in semi-insulating HNPS GaN substrates play a key role in charge transfer as CN, and the work presents a significant advancement in the interpretation of time-dependent photo-EPR measurements.
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