Article
Physics, Applied
Adrian Chmielewski, Ziling Deng, Muad Saleh, Jani Jesenovec, Wolfgang Windl, Kelvin Lynn, John McCloy, Nasim Alem
Summary: The study investigates the atomic and electronic structure of a Hf-doped beta-gallium oxide crystal and finds that Hf dopants prefer octahedral sites and have little impact on the crystal structure. The bandgap values of Hf-doped beta-Ga2O3 are similar to those of unintentionally doped crystals, making Hf an excellent dopant candidate.
APPLIED PHYSICS LETTERS
(2021)
Article
Chemistry, Physical
L. Pan, S. Sholom, S. W. S. McKeever, L. G. Jacobsohn
Summary: This study investigated magnesium aluminum spinels with different Mg:Al ratios for optically stimulated luminescence dosimeters, finding that stoichiometric spinel showed superior OSL dose response, stability, and sensitivity compared to other ratios.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Engineering, Electrical & Electronic
Takaya Sugiura, Nobuhiko Nakano
Summary: The hole impact ionization coefficient of β-Ga2O3 in the <010> direction is determined by numerical simulation. The simulation results are consistent with experimental data and show that hole impact ionization dominates in the breakdown operation of SBD.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Chemistry, Physical
Huaile He, Chao Wu, Haizheng Hu, Shunli Wang, Fabi Zhang, Daoyou Guo, Fengmin Wu
Summary: Previous research has shown that hybridization of N 2p and O 2p orbitals effectively reduces the electrical activity of oxygen vacancies in oxide semiconductors. However, achieving N-alloyed Ga2O3 films, known as GaON, is challenging due to nitrogen's limited solubility in the material. This study explores a new method using plasma-enhanced chemical vapor deposition with high-energy nitrogen plasma to enhance nitrogen solubility. By adjusting the N-2 and O-2 carrier gas ratio, the thin film's bandgap can be tuned, resulting in a decrease in oxygen vacancy density and improved performance of GaON-based photodetectors.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Optics
S. Sholom, S. W. S. McKeever
Summary: Analysis of thermoluminescence (TL) glow curves in aluminosilicate glass shows that the glow curve in the -400 K--600 K region can be partly explained by thermally excited tunneling from a defect excited state to the recombination center. Additionally, a TL signal is observed due to thermal excitation directly to the delocalized band from a distribution of trapping states. Optical bleaching removes the TL signal from this region while producing an optically stimulated luminescence (OSL) signal. The OSL decay curve can be described by optically excited tunneling, along with ionization of trapped electrons directly to the delocalized band.
JOURNAL OF LUMINESCENCE
(2022)
Article
Multidisciplinary Sciences
Marcelo B. Barbosa, Joao Guilherme Correia, Katharina Lorenz, Armandina M. L. Lopes, Goncalo N. P. Oliveira, Abel S. Fenta, Juliana Schell, Ricardo Teixeira, Emilio Nogales, Bianchi Mendez, Alessandro Stroppa, Joao Pedro Araujo
Summary: In this study, Cd dopant was successfully incorporated into the β-Ga2O3 lattice using ion implantation, diffusion, and nuclear transmutation methods. The acceptor nature of Cd in β-Ga2O3 was demonstrated, and a possible approach for contactless charge mobility studies was shown.
SCIENTIFIC REPORTS
(2022)
Article
Nanoscience & Nanotechnology
Drew Haven, Helio Moutinho, John S. Mangum, Harvey Guthrey, David Joyce, Andriy Zakutayev, Nancy M. Haegel
Summary: In this study, the nature of low angle grain boundaries (LAGBs) and the formation of high angle grain boundaries (HAGBs) in beta-Ga2O3 crystals were investigated. Planar LAGBs lying parallel to the (010) plane were found to exist in the region immediately preceding the start of an HAGB. Increased misorientation across the LAGB was observed, approaching the initiation of a new grain. Multimodal microscopy characterization correlated misorientation and variation in optoelectronic properties with LAGBs and the associated dislocations.
Article
Chemistry, Physical
Georgios S. S. Polymeris
Summary: This study attempts to stimulate the deep traps in BeO using thermally assisted optically stimulated luminescence (TA-OSL), and it is found that an intense peak-shaped TA-OSL signal can be measured throughout the temperature range between room temperature and 270 degrees C, suggesting the transfer of charges from deep traps to dosimetric TL traps.
Article
Chemistry, Physical
Motiur R. Khan, Jonas A. Schwenzer, Jonathan Lehr, Ulrich W. Paetzold, Uli Lemmer
Summary: This study investigates the effect of long-term thermal stress on trap states in MAPbI(3) perovskite thin films. It was found that a deep trap level already existed without thermal stress, but an additional deep trap level emerged and grew with thermal stress duration. The variation in trap density with thermal stress time was in line with the trend of open-circuit voltage loss, indicating enhanced nonradiative recombination through these trap states.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Hannah N. Masten, Jamie D. Phillips, Rebecca L. Peterson
Summary: The study found that HfO2/beta-Ga2O3 MOSCAPs exhibited significant positive flatband voltage shifts after stress testing, which could be fully recovered under deep ultraviolet illumination, while HfO2/Si MOSCAPs could not recover and showed smaller voltage shifts. It was also observed that the type-II band alignment between HfO2 and beta-Ga2O3 allowed for full recovery via photogeneration of electron-hole pairs.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2021)
Article
Materials Science, Multidisciplinary
M. Isik, S. Delice, N. M. Gasanly, N. H. Darvishov, V. E. Bagiev
Summary: In this study, the structural properties of Bi12TiO20 single crystal grown by Czochralski method were investigated using X-ray diffraction and scanning electron microscope techniques. The research found that the crystal surface was almost uniform and smooth, with a cubic crystalline structure. Thermally stimulated current experiments revealed the presence of two hole centers in the crystal.
Article
Materials Science, Multidisciplinary
S. Delice, M. Isik, N. M. Gasanly
Summary: Thermally stimulated current (TSC) experiments were performed on Bi12GeO20 single crystals, revealing the existence of trapping levels and their activation energies in the recorded glow curve. The TSC intensity decreased and the peak maximum temperature increased with increasing heating rate.
MATERIALS TODAY COMMUNICATIONS
(2022)
Article
Multidisciplinary Sciences
Hannah L. Stern, Qiushi Gu, John Jarman, Simone Eizagirre Barker, Noah Mendelson, Dipankar Chugh, Sam Schott, Hoe H. Tan, Henning Sirringhaus, Igor Aharonovich, Mete Atature
Summary: In this study, the authors demonstrate optically detected magnetic resonance (ODMR) for single carbon-related defects in hexagonal boron nitride at room temperature, with significantly stronger contrast than the ensemble average. These findings offer a promising route towards realizing a room-temperature spin-photon quantum interface in hexagonal boron nitride.
NATURE COMMUNICATIONS
(2022)
Article
Engineering, Electrical & Electronic
Ahmad Ehteshamul Islam, Chenyu Zhang, Kursti DeLello, David A. Muller, Kevin D. Leedye, Sabyasachi Ganguli, Neil A. Moser, Rachel Kahler, Jeremiah C. Williams, Daniel M. DrydenO, Stephen Tetlak, Kyle J. Liddy, Andrew J. Green, Kelson D. Chabak
Summary: In this article, a method for reducing defect density at the Al2O3/(010) beta-Ga2O3 interface is demonstrated, and the fabricated devices are characterized using current-voltage and capacitance-voltage measurements, showing low hysteresis and consistent performance.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Physics, Multidisciplinary
M. Isik, S. Delice, N. M. Gasanly
Summary: This paper investigates the defect centers in BSO grown by Czochralski method using TSC measurements, revealing the activation energies and peak parameters of intrinsic defect centers through curve fit analyses. The study expands TSC experiments by exploring the heating rate dependent peak parameters.
Article
Physics, Applied
K. Galiano, J. I. Deitz, S. D. Carnevale, D. A. Gleason, P. K. Paul, Z. Zhang, B. M. McSkimming, J. S. Speck, S. A. Ringel, T. J. Grassman, A. R. Arehart, J. P. Pelz
JOURNAL OF APPLIED PHYSICS
(2018)
Article
Physics, Applied
Esmat Farzana, Humberto M. Foronda, Christine M. Jackson, Towhidur Razzak, Zeng Zhang, James S. Speck, Aaron R. Arehart, Steven A. Ringel
JOURNAL OF APPLIED PHYSICS
(2018)
Article
Nanoscience & Nanotechnology
Esmat Farzana, Max F. Chaiken, Thomas E. Blue, Aaron R. Arehart, Steven A. Ringel
Article
Physics, Multidisciplinary
Jared M. Johnson, Zhen Chen, Joel B. Varley, Christine M. Jackson, Esmat Farzana, Zeng Zhang, Aaron R. Arehart, Hsien-Lien Huang, Arda Genc, Steven A. Ringel, Chris G. Van de Walle, David A. Muller, Jinwoo Hwang
Article
Nanoscience & Nanotechnology
Esmat Farzana, Akhil Mauze, Joel B. Varley, Thomas E. Blue, James S. Speck, Aaron R. Arehart, Steven A. Ringel
Article
Nanoscience & Nanotechnology
Hemant Ghadi, Joe F. McGlone, Christine M. Jackson, Esmat Farzana, Zixuan Feng, A. F. M. Anhar Uddin Bhuiyan, Hongping Zhao, Aaron R. Arehart, Steven A. Ringel
Article
Engineering, Electrical & Electronic
Esmat Farzana, Jianfeng Wang, Morteza Monavarian, Takeki Itoh, Kai Shek Qwah, Zachary J. Biegler, Kelsey F. Jorgensen, James S. Speck
IEEE ELECTRON DEVICE LETTERS
(2020)
Article
Physics, Applied
Esmat Farzana, Fikadu Alema, Wan Ying Ho, Akhil Mauze, Takeki Itoh, Andrei Osinsky, James S. Speck
Summary: This study reported high-power application devices using vertical beta-Ga2O3 Schottky diodes grown by MOCVD. The fabricated Schottky diode with field termination structure exhibited low specific on-resistance, suggesting promising performance for high-power beta-Ga2O3-based devices. Compared to other epitaxial growth methods, MOCVD-grown diodes showed better punch-through breakdown and Baliga's figure-of-merit.
APPLIED PHYSICS LETTERS
(2021)
Article
Engineering, Manufacturing
Samuel Kim, Yuewei Zhang, Chao Yuan, Rob Montgomery, Akhil Mauze, Jingjing Shi, Esmat Farzana, James S. Speck, Samuel Graham
Summary: Beta-gallium oxide (β-Ga2O3) is a promising material for power devices with superior properties and device-quality substrates, but requires thermal management strategies due to its low thermal conductivity. Among various cooling strategies, double-side cooling with a heat spreader shows the largest impact on device cooling, reducing thermal resistance and enabling high-power-density vertical CAVET devices. The modeling and analysis results in this study can guide future improvements in beta-Ga2O3 device performance for power electronics applications.
IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING TECHNOLOGY
(2021)
Article
Nanoscience & Nanotechnology
Jianfeng Wang, Kelsey Fast Jorgensen, Esmat Farzana, Kai Shek Qwah, Morteza Monavarian, Zachary J. Biegler, Thomas Mates, James S. Speck
Summary: The study investigates the impact of growth parameters on surface morphology and background doping levels in GaN layers grown using ammonia MBE and plasma-assisted MBE. Results show that MBE is suitable for growing high-quality GaN material with reasonably fast growth rates while maintaining low background doping levels for high-voltage vertical power electronic devices.
Article
Nanoscience & Nanotechnology
Kai Shek Qwah, Esmat Farzana, Ashley Wissel, Morteza Monavarian, Tom Mates, James S. Speck
Summary: We report the improvement of surface morphology of high growth rate c-plane GaN films using ammonia molecular beam epitaxy with the introduction of indium as a surfactant. The indium surfactant enhances adatom mobility, providing smoother growth surfaces. Varying growth parameters results in optimal conditions for surface morphology, reducing roughness and improving overall surface quality. Additionally, indium reduces background impurity concentrations and enables the growth of thick drift layers with low dopant concentrations for vertical GaN power devices.
Article
Nanoscience & Nanotechnology
Esmat Farzana, Arkka Bhattacharyya, Nolan S. Hendricks, Takeki Itoh, Sriram Krishnamoorthy, James S. Speck
Summary: This study presents the use of oxidized-metal contacts and high-kappa dielectric field plate to improve the performance of vertical beta-Ga2O3 Schottky diodes. These modifications enhance the reverse blocking capability, reduce edge leakage current, and enable lower power dissipation, making them promising for high-power applications.
Article
Engineering, Electrical & Electronic
R. M. Cadena, D. R. Ball, E. X. Zhang, S. Islam, A. Senarath, M. W. McCurdy, E. Farzana, J. S. Speck, N. Karom, A. O'Hara, B. R. Tuttle, S. T. Pantelides, A. F. Witulski, K. F. Galloway, M. L. Alles, R. A. Reed, D. M. Fleetwood, R. D. Schrimpf
Summary: Low-energy ion-induced breakdown and single event burnout (SEB) were observed in beta-gallium oxide (beta-Ga2O3) Schottky diodes at voltages lower than expected. Different responses were observed for alpha particles, Cf-252, and heavy-ion irradiation. TCAD simulations explained the breakdown as a result of ion strikes and defect-driven breakdown due to displacement-damage-induced defects in beta-Ga2O3. First-principles calculations showed the formation of less resistive defect clusters that can lead to destruction at reduced voltages.
IEEE TRANSACTIONS ON NUCLEAR SCIENCE
(2023)
Article
Physics, Applied
Esmat Farzana, Saurav Roy, Nolan S. Hendricks, Sriram Krishnamoorthy, James S. Speck
Summary: In this study, PtOx/thin Pt Schottky contacts combined with a high permittivity dielectric (ZrO2) field-plate were used for Schottky barrier engineering in high-voltage vertical beta-Ga2O3 diodes. The results showed that the PtOx/thin Pt/beta-Ga2O3 contact exhibited improved reverse blocking performance and lower turn-on voltage compared to plain metal Pt/beta-Ga2O3 Schottky diodes and plain oxidized metal PtOx/beta-Ga2O3 diodes. Furthermore, the implementation of a high permittivity dielectric field-plate assisted in edge-field management and enabled a higher breakdown voltage. These findings suggest that the PtOx/thin Pt/beta-Ga2O3 Schottky contact, combined with a high permittivity field-plate, has the potential for enabling high-performance and efficient vertical beta-Ga2O3 power switches.
APPLIED PHYSICS LETTERS
(2023)