Article
Chemistry, Multidisciplinary
Hua-Chiang Wen, Ssu-Kuan Wu, Cheng-Wei Liu, Jin-Ji Dai, Wu-Ching Chou
Summary: The nanotribological properties of AlxGa1-xN epitaxial films grown on low-temperature-grown GaN/AlN/Si substrates were investigated. It was found that the Al compositions played a crucial role in determining the strength of bonding forces and shear resistance. The measured friction coefficient (mu) values decreased with increasing Al compositions, indicating a transition from brittleness to ductility in the AlxGa1-xN system.
Article
Chemistry, Physical
Sonachand Adhikari, Olivier Lee Cheong Lem, Felipe Kremer, Kaushal Vora, Frank Brink, Mykhaylo Lysevych, Hark Hoe Tan, Chennupati Jagadish
Summary: The growth of nonpolar m-plane AlGaN on GaN nanowires is limited by the shadowing effect. It is difficult to achieve metal-polar AlGaN nanowires through selective area growth in MOCVD. Nonpolar m-plane GaN nanowires obtained via selective area growth provide an excellent platform for the growth of nonpolar AlGaN MQWs.
Article
Chemistry, Multidisciplinary
Jing Li, Shuang Wang, Qi Jiang, Haoji Qian, Shike Hu, He Kang, Chen Chen, Xiaoyi Zhan, Aobo Yu, Sunwen Zhao, Yanhui Zhang, Zhiying Chen, Yanping Sui, Shan Qiao, Guanghui Yu, Songang Peng, Zhi Jin, Xinyu Liu
Summary: This study successfully achieved the epitaxial growth of single crystal MoS2 (SC-MoS2) monolayer on an Au (111) film, allowing for the unidirectional alignment of MoS2 domains with seamless stitching into a single crystal monolayer without GBs formation. This breakthrough in growth mode provides a new direction for the practical applications of TMDCs in microelectronics.
Article
Materials Science, Multidisciplinary
Vallery Stanishev, Nerijus Armakavicius, Daniela Gogova, Muhammad Nawaz, Niklas Rorsman, Plamen P. Paskov, Vanya Darakchieva
Summary: Hot-wall metal-organic chemical vapor deposition is capable of delivering high-quality n-Al ������Ga1-������N epitaxial layers on 4H-SiC(0001). The layers are crack-free, with low roughness, homogeneous aluminum distribution, and low unintentional incorporation of oxygen and carbon. The electron mobility remains high for Al contents between 0.05 and 0.077, making these layers suitable for power device applications. However, further increase in Al content leads to deterioration of the electrical properties.
Article
Physics, Applied
Shuhei Ichikawa, Mitsuru Funato, Yoichi Kawakami
Summary: The optical anisotropy of r-plane AlxGa1-xN/AlN quantum wells is investigated, and both theoretical calculations and experimental results confirm the polarization switching at a certain Al composition. The polarization property enables the emitted light to propagate in a specific direction and photopumped lasing is demonstrated on a specific structure of quantum wells.
PHYSICAL REVIEW APPLIED
(2022)
Article
Physics, Applied
Kazuki Ohnishi, Seiya Kawasaki, Naoki Fujimoto, Shugo Nitta, Hirotaka Watanabe, Yoshio Honda, Hiroshi Amano
Summary: A vertical GaN p(+)-n junction diode with an ideal breakdown voltage was successfully grown by halide vapor phase epitaxy (HVPE). The steep p(+)-n interface was observed and no Si-accumulating layer was formed due to continuous growth. This method offers improved electrical properties compared to regrowth of p-type GaN layers, with a minimum ideality factor of approximately 1.6.
APPLIED PHYSICS LETTERS
(2021)
Article
Physics, Applied
Caroline E. Reilly, Nirupam Hatui, Thomas E. Mates, Shuji Nakamura, Steven P. DenBaars, Stacia Keller
Summary: This research explores the growth of AlN at temperatures below 550 degrees C via MOCVD using a flow-modulated epitaxy scheme, investigating the morphological, compositional, and electronic properties of the films. The study reveals high sheet charges and mobilities for two dimensional electron gases formed at the interface between the low temperature grown AlN layers and the high temperature deposited semi-insulating GaN base layers. Despite low growth temperatures, unintentional gallium incorporation is observed in nominally pure AlN barrier layers near the GaN interface. These results pave the way for the integration of nitride-based electronics on temperature sensitive substrates via epitaxy-based schemes.
APPLIED PHYSICS LETTERS
(2021)
Article
Chemistry, Physical
M. Camacho-Reynoso, C. A. Hernandez-Gutierrez, C. M. Yee-Rendon, C. Rivera-Rodriguez, D. Bahena-Uribe, S. Gallardo-Hernandez, Yuriy Kudriavtsev, M. Lopez-Lopez, Y. L. Casallas-Moreno
Summary: We report the successful growth of InxGa1-xN/GaN quantum wells in the metastable-cubic phase using two controlled methods, Migration Enhanced Epitaxy (MEE) and conventional Molecular Beam Epitaxy (conventional MBE). The In mole fraction in the c-InxGa1-xN QWs increases as the growth temperature decreases in both methods. The MEE method shows lower In segregation compared to conventional MBE. By varying the In content, excitonic transitions in the visible spectrum range were achieved and matched theoretical calculations. Chemical bonds and binding energies in each c-InxGa1-xN QW were identified using X-ray photoelectron spectroscopy (XPS).
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Multidisciplinary Sciences
William Nunn, Anusha Kamath Manjeshwar, Jin Yue, Anil Rajapitamahuni, Tristan K. Truttmann, Bharat Jalan
Summary: The study introduces a method for atomically precise synthesis of difficult-to-oxidize metal oxide thin films using solid metal-organic compounds, resulting in high-quality Pt and RuO2 films. The approach also demonstrates the feasibility for more complex materials, representing a significant progress in the synthesis science of stubborn materials.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2021)
Article
Physics, Applied
Alexander Polyakov, Vladimir Nikolaev, Sergey Stepanov, Alexei Almaev, Alexei Pechnikov, Eugene Yakimov, Bogdan O. Kushnarev, Ivan Shchemerov, Mikhail Scheglov, Alexey Chernykh, Anton Vasilev, Anastasia Kochkova, Stephen J. Pearton
Summary: This study reports on the growth and electrical properties of alpha-Ga2O3 films grown on alpha-Cr2O3 buffers using halide vapor phase epitaxy. The experimental results showed p-type conductivity of the buffers and low donor ionization energies in Sn-doped alpha-Ga2O3 films prepared on these buffers.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Zhenyu Wang, Mukesh Tripathi, Zahra Golsanamlou, Poonam Kumari, Giuseppe Lovarelli, Fabrizio Mazziotti, Demetrio Logoteta, Gianluca Fiori, Luca Sementa, Guilherme Migliato Marega, Hyun Goo Ji, Yanfei Zhao, Aleksandra Radenovic, Giuseppe Iannaccone, Alessandro Fortunelli, Andras Kis
Summary: In this study, high-quality NbS2-MoS2 lateral heterostructures were synthesized by one-step metal-organic chemical vapor deposition (MOCVD) with Nb substitutionally doped monolayer MoS2, showing p-type doped behavior. The heterojunction exhibited p-type transfer characteristic with a high on/off current ratio of approximately 10^4, surpassing previous reports. The band structure of the NbS2-MoS2 heterojunction was investigated using density functional theory (DFT) and quantum transport simulations. This research provides a scalable approach to synthesize doped TMDC materials and offers insight into the interface between 2D metals and semiconductors in lateral heterostructures, which is crucial for the development of next-generation nanoelectronics and highly integrated devices.
ADVANCED MATERIALS
(2023)
Article
Crystallography
Masatomo Sumiya, Yuki Takahara, Amira Alghamdi, Yoshiko Nakayama, Fumihiko Uesugi, Yoshitomo Harada, Akira Uedono, Yasutaka Imanaka
Summary: Successful fabrication of AlGaN/GaN and AlGaN/InGaN/GaN heterostructures was achieved, with important implications for controlling the carrier density of two-dimensional electron gas. In the AlGaN/InGaN/GaN system, defined surface morphology and alloy disorder on InGaN, but significantly degraded mobility of 2DEG was observed.
JOURNAL OF CRYSTAL GROWTH
(2021)
Article
Physics, Condensed Matter
Rashmi Rani, William Maudez, Rajat Sayal, Radheshyam Rai, Sanjeev Kumar, Md Kashif Shamim, Estelle Wagner, Seema Sharma, Giacomo Benvenuti
Summary: HfO2 thin films with three different thicknesses (-10 nm, -30 nm & - 50 nm) were deposited on TiN/Si using the CBVD technique. The structural, morphological, and dielectric properties of the films were extensively studied. The results showed that the films had a stable monoclinic phase regardless of thickness, and exhibited homogeneous and crack-free surfaces according to atomic force microscopy (AFM) analysis. The dielectric constant reached a maximum value at room temperature (up to -67) at 2 kHz, which was three times higher than previously reported values.
PHYSICA B-CONDENSED MATTER
(2023)
Article
Physics, Applied
Abhiram Gundimeda, Martin Frentrup, Simon M. Fairclough, Menno J. Kappers, David J. Wallis, Rachel A. Oliver
Summary: The influence of AlGaN nucleation layers on zincblende GaN epilayers and the formation of wurtzite phase inclusions in the epilayer were studied. It was found that an increase in aluminum content in the AlGaN nucleation layer leads to an increased presence of wurtzite inclusions. The strong {111}-type faceting observed in the zincblende nucleation layer on an Al0.29Ga0.71N nucleation layer contributes to the formation of wurtzite inclusions at the GaN/ Al0.29Ga0.71N interface.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Ding Wang, Shubham Mondal, Jiangnan Liu, Mingtao Hu, Ping Wang, Samuel Yang, Danhao Wang, Yixin Xiao, Yuanpeng Wu, Tao Ma, Zetian Mi
Summary: We demonstrate ferroelectric switching in yttrium-doped nitride semiconductors. Yttrium 0.07Al0.93N films were grown on GaN/sapphire templates and exhibited a coercive field of 6 MV/cm and a switchable polarization of 130 mu C/cm(2). Ferroelectric switching was confirmed through capacitance-voltage loops and polarity-sensitive wet etching. This study expands the family of nitride ferroelectrics and opens up possibilities for applications in III-nitride based devices.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Jian-Sian Li, Chao-Ching Chiang, Xinyi Xia, Sergei Stepanoff, Aman Haque, Douglas E. Wolfe, Fan Ren, S. J. Pearton
Summary: NiO/Ga2O3 heterojunction rectifiers were irradiated with 1 Mrad of Co-60 gamma-rays, resulting in a 1000x reduction in forward current, a 100x increase in reverse current, and a significant decrease in the on-off ratio. The carrier concentration in the Ga2O3 drift region slightly decreased, indicating a reversible effect. The rectifiers showed no permanent ionizing dose effects and resistance to displacement damage, suggesting potential applications in harsh radiation environments with appropriate bias sequences.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Materials Science, Coatings & Films
Jian-Sian Li, Xinyi Xia, Chao-Ching Chiang, David C. C. Hays, Brent P. P. Gila, Valentin Craciun, Fan Ren, S. J. Pearton
Summary: The characteristics of sputtered NiO for pn heterojunctions with Ga2O3 were investigated, and it was found that the oxygen/nickel and Ni2O3/NiO ratios, as well as the bandgap and resistivity, increased with the O-2/Ar gas flow ratio. However, the bandgap and Ni2O3/NiO ratio decreased with increasing annealing temperature, resulting in higher film density. The incorporation of hydrogen into NiO during plasma exposure was confirmed, and the band alignments of NiO films with both alpha- and beta-Ga2O3 were determined to have type II-staggered gaps. The breakdown voltage of NiO/beta-Ga2O3 heterojunction rectifiers also varied with the O-2/Ar flow ratio during deposition.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Materials Science, Coatings & Films
Benjamin C. Letson, Simon Barke, Peter Wass, Guido Mueller, Fan Ren, Stephen J. Pearton, John W. Conklin
Summary: The laser interferometer space antenna (LISA), a joint ESA and NASA project, will enable space-based gravitational wave detection. Three identical spacecraft will form a triangular configuration, flying in a drag-free formation around free-falling test masses. To compensate for test mass charging, UV photons with higher energy than gold's work function are needed. The performance of UV light emitting diodes (LEDs) for the LISA mission was characterized under various operating conditions, and degradation was found to be faster at elevated temperatures and in dc conditions. Preselection based on initial spectral ratio and ideality factor showed positive correlation with subsequent reliability. The UV LEDs for LISA are required to support a 2-year cruise and commissioning period, followed by a 4-year science mission.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Engineering, Electrical & Electronic
Chao-Ching Chiang, Chan-Wen Chiu, Fan Ren, Cheng-Tse Tsai, Yu-Te Liao, Josephine F. Esquivel-Upshaw, Stephen J. Pearton
Summary: This study presents a SARS-CoV-2 virus detection mechanism using stored disposable strips. The accuracy of this sensing platform is comparable to PCR and provides results in less than 30 seconds. The disposable strips, biofunctionalized with SARS-CoV-2 antibodies, detect the virus in saliva samples, and the detected signals are amplified and displayed on an LCD screen. The system demonstrates the ability to show qualitative results within 30 seconds and quantitative concentrations in 5 minutes.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B
(2023)
Article
Engineering, Electrical & Electronic
Minghan Xian, Jenna L. Stephany, Chan-Wen Chiu, Chao-Ching Chiang, Fan Ren, Cheng-Tse Tsai, Siang-Sin Shan, Yu-Te Liao, Josephine F. Esquivel-Upshaw, Stephen J. Pearton
Summary: Oral squamous cell carcinoma is a common type of lip and oral cavity cancer, which requires early detection for improved survival rates. A modular biological sensor utilizing transistor-based technology has been developed for rapid and accurate point of care detection of the cancer, providing opportunities for quick clinical diagnosis.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B
(2023)
Article
Physics, Applied
Md Abu Jafar Rasel, Nahid Sultan Al-Mamun, Sergei Stepanoff, Aman Haque, Douglas E. Wolfe, Fan Ren, Stephen J. Pearton
Summary: In this work, we illustrate the rejuvenation of degraded Ti/4H-SiC Schottky barrier diodes at room temperature within seconds by utilizing high-energy electron interactions with defects. By applying high current density electrical pulsing with low frequency and duty cycle to suppress temperature rise, we successfully decrease defect concentration and improve device performance beyond the pristine condition. The ultrafast and room temperature process has the potential to rejuvenate electronic devices in high power and harsh environmental conditions.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
A. Y. Polyakov, A. I. Kochkova, A. Azarov, V. Venkatachalapathy, A. V. Miakonkikh, A. A. Vasilev, A. V. Chernykh, I. V. Shchemerov, A. A. Romanov, A. Kuznetsov, S. J. Pearton
Summary: Ion beam fabrication of metastable polymorphs of Ga2O3, assisted by the controllable accumulation of the disorder in the lattice, is explored for its alternative approach to conventional deposition techniques. In this study, two strategies - ion implantation of silicon donors and plasma treatment with hydrogen - are investigated for tuning the electron concentration in the ion beam created metastable kappa-polymorph. The results show that silicon doping did not change the high resistive state, while hydrogen plasma treatment converted the ion beam fabricated kappa-polymorph to n-type conductivity.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Md Abu Jafar Rasel, Ryan Schoell, Nahid Sultan Al-Mamun, Khalid Hattar, C. Thomas Harris, Aman Haque, Douglas E. Wolfe, Fan Ren, Stephen J. Pearton
Summary: This study investigated the effects and mechanism of IL-37 on pyroptosis in RA-FLSs induced by TNF-a. It was found that IL-37 inhibited inflammation and reduced pyroptosis-related protein expression in RA-FLSs. The study also revealed that IL-37 alleviates TNF-a-induced pyroptosis in RA-FLSs by inhibiting NF-?B/GSDMD signaling.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Materials Science, Coatings & Films
A. Y. Polyakov, A. I. Kochkova, Amanda Langorgen, Lasse Vines, A. Vasilev, I. V. Shchemerov, A. A. Romanov, S. J. Pearton
Summary: The study investigates the relationship between the emission rate of deep traps called E1 traps and the electric field dependence. The results demonstrate that the activation energy of the centers and the ratio of high-field to low-field electron emission rates follow a linear relationship with the square root of electric field at a fixed temperature, indicating the deep donor behavior of these traps. The possible microscopic nature of these centers is discussed based on recent theoretical calculations, and the most likely candidates are proposed to be Si-Ga1-H or Sn-Ga2-H complexes.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Review
Materials Science, Multidisciplinary
Benjamin C. Letson, John W. Conklin, Peter Wass, Simon Barke, Guido Mueller, Md Abu Jafar Rasel, Aman Haque, Stephen J. Pearton, Fan Ren
Summary: There are various applications for deep UV AlGaN Light-Emitting Diodes (LEDs), including virus inactivation, air and water purification, sterilization, bioagent detection, and UV polymer curing. The long-term stability of these LEDs is important for space missions such as the Laser Interferometer Space Antenna (LISA). The literature review shows that the decline in output power of these LEDs over extended operating times is mainly driven by current and temperature, with the degradation rate dependent on the cube of drive current density and exponentially on temperature. The main mechanism for this decline is believed to be the creation/migration of point defects. Pre-screening based on the ratio of band edge-to-midgap emission and LED ideality factor can identify devices with long lifetimes (>10,000 h).
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2023)
Article
Crystallography
Jian-Sian Li, Hsiao-Hsuan Wan, Chao-Ching Chiang, Xinyi Xia, Timothy Jinsoo Yoo, Honggyu Kim, Fan Ren, Stephen J. Pearton
Summary: Vertical heterojunction rectifiers with p-type NiO and thick Ga2O3 drift layers grown on Sn-doped β-Ga2O3 substrates exhibited breakdown voltages > 8 kV. Low drift doping concentration, low power during NiO deposition, and the formation of a guard ring were key factors for achieving excellent performance. These results demonstrate the potential of NiO/Ga2O3 rectifiers beyond SiC and GaN.
Article
Materials Science, Multidisciplinary
Jian-Sian Li, Xinyi Xia, Chao-Ching Chiang, Hsiao-Hsuan Wan, Fan Ren, Jihyun Kim, S. J. Pearton
Summary: Neutrons generated by charge-exchange reactions were used to irradiate Schottky Ga2O3 rectifiers and NiO/Ga2O3 p-n heterojunction rectifiers. The breakdown voltage was improved for Schottky rectifiers but highly degraded for their NiO/Ga2O3 counterparts. The switching characteristics were degraded for both types of devices after irradiation.
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2023)
Article
Materials Science, Multidisciplinary
Jian-Sian Li, Chao-Ching Chiang, Xinyi Xia, Hsiao-Hsuan Wan, Fan Ren, S. J. Pearton
Summary: Large area vertical NiO/β n-Ga2O/n(+) Ga2O3 heterojunction rectifiers with high breakdown voltage (3.6 kV) and large conducting currents (4.8 A) are demonstrated. The performance exceeds the unipolar 1D limit for GaN, indicating the potential of β-Ga2O3 for future high-power rectification devices. The breakdown voltage is strongly dependent on the carrier concentration in the drift region.
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2023)
Article
Materials Science, Multidisciplinary
Jian-Sian Li, Chao-Ching Chiang, Xinyi Xia, Hsiao-Hsuan Wan, Fan Ren, S. J. Pearton
Summary: NiO/β-Ga2O3 vertical rectifiers show near-temperature-independent breakdown voltages (V-B) of >8 kV at 600 K. The power figure of merit (V-B)²/R-ON for 100 μm diameter devices is 9.1 GW cm(-2) at 300 K and 3.9 GW cm(-2) at 600 K. In contrast, Schottky rectifiers on the same wafers have V-B of about 1100 V at 300 K with a negative temperature coefficient of breakdown. The power figure of merit for Schottky rectifiers is much lower compared to the heterojunction rectifiers. The results demonstrate the potential of using transparent oxide heterojunctions for high temperature, high voltage applications.
JOURNAL OF MATERIALS CHEMISTRY C
(2023)
Review
Engineering, Electrical & Electronic
S. J. Pearton, Xinyi Xia, Fan Ren, Md Abu Jafar Rasel, Sergei Stepanoff, Nahid Al-Mamun, Aman Haque, Douglas E. Wolfe
Summary: Wide bandgap semiconductors SiC and GaN are used in power electronics and light-emitting diodes. They have higher radiation hardness compared to Si devices due to larger threshold energies for creating defects and high rates of defect recombination. However, heavy-ion-induced catastrophic burnout commonly occurs in SiC and GaN power devices. Light-emitting devices are not affected by this mechanism. Strain has also been identified as a parameter affecting radiation susceptibility of wide bandgap devices.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B
(2023)