Dr. Ümit Özgür Profile

Dr. Ümit Özgür

Professor at Virginia Commonwealth Univ

SPIE Involvement:

Conference Program Committee | Author

Publications (88)

Proceedings Article | 16 March 2023 Presentation

Investigation of plasmonic losses in TCOs based on heavily doped ZnO (Conference Presentation)

Vitaliy Avrutin, Dhruv Fomra, Nathaniel Kinsey, Natalia Izyumskaya, Ümit Özgür, Hadis Morkoç, Martin Feneberg, Ruediger Goldhahn

Proceedings Volume PC12422, PC1242211 (2023) https://doi.org/10.1117/12.2661314

KEYWORDS: Plasmonics, Zinc oxide, Atomic layer deposition, Transparent conductors, Thin films, Spectroscopic ellipsometry, Infrared spectroscopy, X-ray diffraction, Transparent conducting oxide, Thin film deposition

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Proceedings Article | 16 March 2023 Presentation

High-field electron transport and microwave noise in ZnO channels with 2 dimensional electron gas (Conference Presentation)

Vitaliy Avrutin, Ümit Özgür, Hadis Morkoç, Linas Ardaravičius, Arthur Šimukovič, Emilis Šermukšnis

Proceedings Volume PC12422, PC124220K (2023) https://doi.org/10.1117/12.2661416

KEYWORDS: Electron transport, Microwave radiation, Zinc oxide, Resistance, Temperature metrology, Phonons, Molecular beam epitaxy, Heterojunctions

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Proceedings Article | 16 March 2023 Presentation + Paper

Demonstration of thick phase-pure β-Ga2O3 on a c-plane sapphire substrate using MOCVD

Mohi Uddin Jewel, Samiul Hasan, Scott Crittenden, Vitaliy Avrutin, Ümit Özgür, Hadis Morkoç, Iftikhar Ahmad

Proceedings Volume 12422, 1242204 (2023) https://doi.org/10.1117/12.2661097

KEYWORDS: Gallium, Annealing, Sapphire, Metalorganic chemical vapor deposition, Silicon, Thin films, Surface roughness, Semiconductors, Gallium oxide, Reflection

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Proceedings Article | 15 March 2023 Presentation + Paper

Gate leakage current and threshold voltage characteristics of β-Ga2O3 passivated AlGaN/GaN based heterojunction field effect transistor

Samiul Hasan, Mohi Uddin Jewel, Scott Crittenden, Dongkyu Lee, Vitaliy Avrutin, Ümit Özgür, Hadis Morkoç, Iftikhar Ahmad

Proceedings Volume 12421, 124210A (2023) https://doi.org/10.1117/12.2668236

KEYWORDS: Dielectrics, Gallium nitride, Heterojunctions, Field effect transistors, Oxides, Passivation, Gallium, Metalorganic chemical vapor deposition, Interfaces, Capacitance

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Proceedings Article | 3 October 2022 Presentation

Dual excitation beam deflection in nonlinear epsilon-near-zero materials

Adam Ball, Ray Secondo, Dhruv Fomra, Vitaly Avrutin, Umit Ozgur, Nathaniel Kinsey

Proceedings Volume PC12228, PC122280J (2022) https://doi.org/10.1117/12.2632849

KEYWORDS: Refractive index, Absorption, Plasma, Modulation, Zinc oxide, Ultraviolet radiation, Process control, Nonlinear response, Nonlinear optics, Electrons

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Proceedings Article | 3 October 2022 Presentation

Nonlinearities when the index vanishes

Nathaniel Kinsey, Adam Ball, Dhruv Fomra, Ray Secondo, Jingwei Wu, Mohammad A. Sojib, Samprity Saha, Vitaliy Avrutin, Umit Ozgur

Proceedings Volume PC12196, PC1219603 (2022) https://doi.org/10.1117/12.2633454

KEYWORDS: Refractive index, Harmonic generation, Absorption

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Proceedings Article | 5 March 2022 Presentation

Beam deflection characterization of nonlinear TCOs at ENZ

Adam Ball, Ray Secondo, Dhruv Fomra, Vitaly Avrutin, Umit Ozgur, Nate Kinsey

Proceedings Volume PC12002, PC120020V (2022) https://doi.org/10.1117/12.2623600

KEYWORDS: Transparent conducting oxide, Oxides, Optical testing, Zinc oxide, Tin, Sensors, Refractive index, Light-matter interactions, Laser beam diagnostics, Indium

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Proceedings Article | 3 August 2021 Presentation

Epsilon-near-zero materials in nonlinear optics: from theory to applications

Nathaniel Kinsey, Ray Secondo, Dhruv Fomra, Adam Ball, Mohammad A. Sojib, Kai Ding, Vitaliy Avrutin, Umit Ozgur, Jacob Khurgin

Proceedings Volume 11796, 117960S (2021) https://doi.org/10.1117/12.2594197

KEYWORDS: Nonlinear optics, Atomic layer deposition, Modulation, Thin films, Switching, Metamaterials, Integrated photonics, Doping, Deposition processes

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Proceedings Article | 5 March 2021 Presentation

DC and microwave performance of BeMgZnO/ZnO heterostructure field effect transistors

Kai Ding, Vitaliy Avrutin, Natalia Izyumskaya, Ümit Özgür, Hadis Morkoç, Emilis Šermukšnis, Arvydas Matulionis

Proceedings Volume 11687, 116871D (2021) https://doi.org/10.1117/12.2586813

KEYWORDS: Heterojunctions, Field effect transistors, Microwave radiation, Zinc oxide, Sapphire, Plasmons, Fourier transforms, Dielectrics

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Proceedings Article | 5 March 2021 Presentation

Comparative study of MBE- and ALD-deposited doped zinc oxide

Dhruv Fomra, Kai Ding, Vitaliy Avrutin, Ümit Özgür, Nathaniel Kinsey

Proceedings Volume 11687, 1168711 (2021) https://doi.org/10.1117/12.2588695

KEYWORDS: Zinc oxide, Atomic layer deposition, Sapphire, Transparent conducting oxide, Slow light, Refractive index, Photonic integrated circuits, Molecular beam epitaxy, Gallium

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Proceedings Article | 20 August 2020 Presentation

All oxide plasmon-assisted optical modulator

Dhruv Fomra, Vitaliy Avrutin, Ümit Özgür, Nathaniel Kinsey

Proceedings Volume 11461, 114611U (2020) https://doi.org/10.1117/12.2568526

KEYWORDS: Optical modulators, Oxides, Modulation, Plasmonics, Modulators, Capacitors, Internet, Video, Data centers, Software engineering

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Proceedings Article | 20 August 2020 Presentation

Plasmonic color using titanium nitride for robust security devices

Dhruv Fomra, Md Ataul Mamun, Kai Ding, Vitaliy Avrutin, Ümit Özgür, Nathaniel Kinsey

Proceedings Volume 11462, 114621H (2020) https://doi.org/10.1117/12.2568547

KEYWORDS: Plasmonics, Silver, Tin, Titanium, Computer security, Gold, Aluminum, Plasma, Visible radiation, Surface plasmons

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Proceedings Article | 10 March 2020 Presentation

Low-temperature growth of Al-doped ZnO by atomic layer deposition for plasmonics (Conference Presentation)

Dhruv Fomra, Kai Ding, Vitaliy Avrutin, Natalia Izyumskaya, Nathaniel Kinsey, Ümit Özgür, Hadis Morkoç

Proceedings Volume 11281, 1128119 (2020) https://doi.org/10.1117/12.2550537

KEYWORDS: Atomic layer deposition, Plasmonics, Zinc oxide, Aluminum, Telecommunications, Transparent conducting oxide, Sapphire, Molecular beam epitaxy, Crystals, Gallium

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Proceedings Article | 5 March 2020 Presentation + Paper

Molecular beam epitaxy of Zn-polar ZnO/BeMgZnO heterostructure field effect transistors on GaN and c-sapphire: a comparative study

Kai Ding, Vitaliy Avrutin, Natalia Izyumskaya, Ümit Özgür, Hadis Morkoç

Proceedings Volume 11281, 112811Q (2020) https://doi.org/10.1117/12.2550534

KEYWORDS: Zinc oxide, Gallium nitride, Sapphire, Heterojunctions, Molecular beam epitaxy, Field effect transistors, Metalorganic chemical vapor deposition, Electronics, Semiconductors, Polarization

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Proceedings Article | 16 February 2020 Paper

PECVD grown SiN photonic crystal micro-domes for the light extraction enhancement of GaN LEDs

M. Genç, V. Sheremet, İ. Altuntaş, İ. Demir, E. Gür, S. Elagöz, O. Gülseren, Ü. Özgür, V. Avrutin, H. Morkoç, A. Aydınlı

Proceedings Volume 11280, 112800O (2020) https://doi.org/10.1117/12.2547206

KEYWORDS: Light emitting diodes, Silver, Photonic crystals, Gallium nitride, Sapphire, Plasma enhanced chemical vapor deposition, Silicon, Refractive index, Reflection, Light scattering

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Proceedings Article | 1 March 2019 Presentation + Paper

Electrical properties of BeMgZnO/ZnO heterostructures with high-density two-dimensional electron gas

K. Ding, V. Avrutin, N. Izyumskaya, Ü. Özgür, H. Morkoç, E. Šermukšnis, A. Matulionis

Proceedings Volume 10919, 1091917 (2019) https://doi.org/10.1117/12.2511644

KEYWORDS: Heterojunctions, Magnesium, Beryllium, Zinc oxide, Phonons, Zinc, Profiling, Interfaces, Gallium nitride, Oxygen

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Proceedings Article | 17 September 2018 Presentation

Characterization of plasma enhanced atomic layer deposited titanium nitride (Conference Presentation)

Ray Secondo, Dhurv Fomra, Natalia Izyumskaya, Vitally Avrutin, Ümit Özgür, Nathaniel Kinsey

Proceedings Volume 10720, 107200M (2018) https://doi.org/10.1117/12.2321132

KEYWORDS: Atomic layer deposition, Plasma, Titanium, Tin, Optical properties, Silicon films, Plasmonics, Sputter deposition, Sapphire, Silicon

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Proceedings Article | 14 May 2018 Paper

Finite size narrow-band transmission filters for real-time short wave IR spectroscopy and imaging

Ryan Green, Vitaliy Avrutin, Ümit Özgür, Nibir Dhar, Erdem Topsakal

Proceedings Volume 10656, 106561U (2018) https://doi.org/10.1117/12.2304665

KEYWORDS: Optical filters, Imaging spectroscopy, Dielectrics, Short wave infrared radiation, Dielectric filters, Image filtering, Infrared spectroscopy, Infrared imaging, Spectroscopy, Fabry–Perot interferometers

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Proceedings Article | 23 February 2018 Presentation + Paper

Recent progress in nonpolar and semi-polar GaN light emitters on patterned Si substrates

K. Ding, V. Avrutin, N. Izyumskaya, S. Metzner, F. Bertram, J. Christen, U. Ozgur, H. Morkoc

Proceedings Volume 10532, 1053208 (2018) https://doi.org/10.1117/12.2291281

KEYWORDS: Gallium nitride, Silicon, Light emitting diodes, Indium gallium nitride, Crystals, Scanning electron microscopy, Indium, Polarization, Optical properties, Interfaces

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Proceedings Article | 24 February 2017 Paper

Quaternary BeMgZnO by plasma-enhanced molecular beam epitaxy for BeMgZnO/ZnO heterostructure devices

M. B. Ullah, M. Toporkov, V. Avrutin, Ü. Özgür, D. Smith, H. Morkoç

Proceedings Volume 10105, 101050J (2017) https://doi.org/10.1117/12.2260814

KEYWORDS: Heterojunctions, Molecular beam epitaxy, Zinc oxide, Field effect transistors, Magnesium, Beryllium, Zinc, Polarization, Crystals, Gallium nitride, Transmission electron microscopy

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We investigated the crystal structure, growth kinetics and electrical properties of BeMgZnO/ZnO heterostructures grown by Molecular Beam Epitaxy (MBE). Transmission Electron Microscopy (TEM) studies revealed that incorporation of Mg into the BeZnO solid solution eliminates the high angle grain boundaries that are the major structural defects in ternary BeZnO. The significant improvement of x-ray diffraction intensity from quaternary BeMgZnO alloy compared to ternary BeZnO was attributed to the reduction of lattice strain, which is present in the latter due to the large difference of covalent radii between Be and Zn (1.22 Å for Zn, 0.96 Å for Be). Incorporation of Mg, which has a larger covalent radius of 1.41Å, reduced the strain in BeMgZnO thin films and also enhanced Be incorporation on lattice sites in the wurtzite lattice. The Zn/(Be + Mg) ratio necessary to obtain single-crystal O-polar BeMgZnO on (0001) GaN/sapphire templates was found to increase with increasing substrate temperature:3.9, 6.2, and 8.3 at substrate temperatures of 450°C, 475°C, and 500°C, respectively. Based on analysis of photoluminescence spectra from Be_0.03Mg_yZn_0.97-yO and evolution of reflection high-energy electron diffraction patterns observed in situ during the MBE growth, it has been deduced that more negative formation enthalpy of MgO compared to ZnO and the increased surface mobility of Mg adatoms at elevated substrate temperatures give rise to the nucleation of a MgO-rich wurtzite phase at relatively low Zn/(Be + Mg) ratios. We have demonstrated both theoretically and experimentally that the incorporation of Be into the barrier in Zn-polar BeMgZnO/ZnO and O-polar ZnO/BeMgZnO polarization doped heterostructures allows the alignment of piezoelectric polarization vector with that of spontaneous polarization due to the change of strain sign, thus increasing the amount of net polarization. This made it possible to achieve Zn-polar BeMgZnO/ZnO heterostructures grown on GaN/sapphire templates with two-dimensional electron gas densities substantially exceeding those in Zn-polar MgZnO/ZnO and O-polar ZnO/MgZnO heterostructures with similar Mg content.

Proceedings Article | 27 February 2016 Paper

Exciton localization and large Stokes shift in quaternary BeMgZnO grown by molecular beam epitaxy

Mykyta Toporkov, Md. Barkat Ullah, Shopan Hafiz, Tanner Nakagawara, Vitaliy Avrutin, Hadis Morkoç, Ümit Özgür

Proceedings Volume 9749, 974910 (2016) https://doi.org/10.1117/12.2214156

KEYWORDS: Excitons, Thin films, Molecular beam epitaxy, Luminescence, Optoelectronic devices, Carrier dynamics, Zinc oxide, Solids, Ultraviolet radiation, Optoelectronics, Magnesium, Beryllium, Gallium nitride, Absorption, Zinc, Sapphire

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Owing to wide range bandgap tunability to more than 5 eV, the quaternary (Be,Mg)ZnO solid solutions are attractive for a variety of UV optoelectronic applications, inclusive of solar blind photodetectors, and intersubband transition devices. The mutual compensation effects of Be and Mg on the formation energy and strain allows a wide range of compositions and bandgaps beyond those achievable by MgZnO and BeZnO ternaries. Localization effects are well pronounced in such wide-bandgap semiconductor alloys due to large differences in metal covalent radii and the lattice constants of the binaries, resulting in strain-driven compositional variations within the film and consequently large potential fluctuations, in addition to that possibly caused by defects. However, carrier localization may suppress recombination through nonradiative channels, and thus, facilitate high-efficiency optoelectronic devices. To investigate potential fluctuations and localization in Be_xMg_yZn(_1-x-y)O films grown by plasma-assisted molecular beam epitaxy, optical absorption and steady-state and time-resolved photoluminescence (PL) measurements were performed. O-polar Be_xMg_yZn(_1-x-y)O samples grown on GaN templates with compositions up to x = 0.04 and y = 0.18 were used for timeresolved studies, and O-polar Be_xMg_yZn(_1-x-y)O samples grown on sapphire with compositions up to x = 0.19 and y = 0.52 were used for absorption measurements. From spectrally resolved PL transients, BeMgZnO samples with higher Mg/Be content ratio were found to exhibit smaller localization depth, Δ₀=98 meV for Be_0.04Mg_0.17Zn_0.79O and Δ₀=173 meV for Be_0.10Mg_0.25Zn_0.65O, compared to samples with smaller Mg/Be ratio, Δ₀=268 meV for Be_0.11Mg_0.15Zn_0.74O. Similar correlation is observed in temporal redshift of the PL peak position of 8 meV, 42 meV and 55 meV for Be_0.04Mg_0.17Zn_0.79O, Be_0.10Mg_0.25Zn_0.65O and Be_0.11Mg_0.15Zn_0.74O, respectively, that originates from potential fluctuations and removal of band filling effect in the localized states. PL transients indicate that emission at low temperature is dominated by recombination of localized excitons, which exhibit decay times as long as τ = 0.36 ns at the peak position. The Sshaped behavior of PL peak with change in temperature was observed for the quaternary alloy Be_0.04Mg_0.17Zn_0.79O. The degree of localization σ was determined to be 22 meV. Relatively high potential fluctuations and localization energy lead to a strong Stokes shift, which increased with bandgap reaching ~0.5 eV for O-polar BeMgZnO on sapphire with 4.6 eV absorption edge.

Proceedings Article | 26 February 2016 Paper

Enhancement of indium incorporation to InGaN MQWs on AlN/GaN periodic multilayers

Morteza Monavarian, Shopan Hafiz, Saikat Das, Natalia Izyumskaya, Ümit Özgür, Hadis Morkoç, Vitaliy Avrutin

Proceedings Volume 9748, 974825 (2016) https://doi.org/10.1117/12.2213777

KEYWORDS: Indium gallium nitride, Indium, Gallium nitride, Luminescence, Heterojunctions, Quantum wells, X-ray diffraction, Aluminum nitride, Nanostructures, Quantum efficiency, Indium nitride, Satellites, Gallium

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Proceedings Article | 26 February 2016 Paper

Exciton localization in (11-22)-oriented semi-polar InGaN multiple quantum wells

Morteza Monavarian, Daniel Rosales, Bernard Gil, Natalia Izyumskaya, Saikat Das, Ümit Özgür, Hadis Morkoç, Vitaliy Avrutin

Proceedings Volume 9748, 974826 (2016) https://doi.org/10.1117/12.2213835

KEYWORDS: Excitons, Indium gallium nitride, Quantum wells, Luminescence, Quantum efficiency, Gallium nitride, Heterojunctions, Epitaxial lateral overgrowth, Temperature metrology, Picosecond phenomena, Indium, Lab on a chip, Light emitting diodes, Gallium

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Proceedings Article | 26 February 2016 Paper

Wurtzite/zinc-blende electronic-band alignment in basal-plane stacking faults in semi-polar GaN

Morteza Monavarian, Shopan Hafiz, Natalia Izyumskaya, Saikat Das, Ümit Özgür, Hadis Morkoç, Vitaliy Avrutin

Proceedings Volume 9748, 974827 (2016) https://doi.org/10.1117/12.2213859

KEYWORDS: Gallium nitride, Interfaces, Ultrafast phenomena, Polarization, Optical spectroscopy, Spectroscopy, Femtosecond phenomena, Electrons, Quantum wells, Picosecond phenomena, Scanning transmission electron microscopy, Laser beam diagnostics, Sapphire, Excitons

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Proceedings Article | 26 February 2016 Paper

Optical investigation of microscopic defect distribution in semi-polar (1-101 and 11-22) InGaN light-emitting diodes

Shopan Hafiz, Nicolas Andrade, Morteza Monavarian, Natalia Izyumskaya, Saikat Das, Fan Zhang, Vitaliy Avrutin, Hadis Morkoç, Ümit Özgür

Proceedings Volume 9748, 974828 (2016) https://doi.org/10.1117/12.2213908

KEYWORDS: Light emitting diodes, Near field optics, Near field scanning optical microscopy, Indium gallium nitride, Luminescence, Epitaxial lateral overgrowth, Nanostructures, Gallium nitride, Indium, Scanning electron microscopy, Quantum efficiency

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