Article
Nanoscience & Nanotechnology
Luke A. M. Lyle, Tyson C. Back, Cynthia T. Bowers, Andrew J. Green, Kelson D. Chabak, Donald L. Dorsey, Eric R. Heller, Lisa M. Porter
Summary: Chemical and electrical measurements of Ti/(010) beta-Ga2O3 and Ti/(001) beta-Ga2O3 interfaces were conducted with XPS, J-V, and C-V measurements as a function of annealing temperature. The results show that the reactivity of Ti on the beta-Ga2O3 surface strongly affects the electrical performance and stability of Ti/beta-Ga2O3 ohmic contacts at elevated temperatures. The oxidized Ti amount increased with annealing temperature, and the Schottky barrier height had variations with temperature changes.
Article
Nanoscience & Nanotechnology
Ming-Hsun Lee, Ta-Shun Chou, Saud Bin Anooz, Zbigniew Galazka, Andreas Popp, Rebecca L. Peterson
Summary: The effect of post-metallization anneal temperature on Ti/Au ohmic contact performance for (100)-oriented Ga2O3 was investigated. An optimal anneal temperature of around 420°C resulted in low contact resistance, but a drastic degradation occurred at 520°C with the formation of GaAu2 inclusions and an expanded Ti-TiOx interfacial layer at the degraded ohmic contact site. The findings emphasize the critical influence of Ga2O3 anisotropy on the optimal post-metallization anneal temperature and suggest the need for alternative metallization schemes for gallium oxide.
Article
Computer Science, Information Systems
Peipei Ma, Jun Zheng, Yabao Zhang, Zhi Liu, Yuhua Zuo, Buwen Cheng
Summary: Heavy doped n-type beta-Ga2O3 (HD-Ga2O3) was obtained by Si ion implantation on unintentionally doped beta-Ga2O3 single crystal substrates. The ion-implanted layer showed high lattice quality after high-temperature annealing, and the minimum specific contact resistance was reduced by the formation of titanium oxide at the Ti/Ga2O3 interface. Lateral beta-Ga2O3 diodes prepared using HD-Ga2O3 exhibited high forward current density and low specific on-resistance.
TSINGHUA SCIENCE AND TECHNOLOGY
(2023)
Article
Chemistry, Physical
Linpeng Dong, Shun Zhou, Kaiwen Pu, Chen Yang, Bin Xin, Bo Peng, Weiguo Liu
Summary: The study investigated the electronic properties of ML Ga2O3 FETs with different metal electrodes using energy band structure and quantum transport calculations. The results show that Al electrode exhibits the highest performance with Ohmic contact property and absence of a tunneling barrier, making it the best candidate electrode material for ML Ga2O3 transistors.
APPLIED SURFACE SCIENCE
(2021)
Article
Chemistry, Physical
Fei Cao, Yang-xi Xu, Jin-chi Sui, Xing-ji Li, Jian-qun Yang, Ying Wang
Summary: This paper investigates the electrical and structural properties of Cu/Ti/Al ohmic contacts to p-type 4H-SiC with different annealing temperatures and Cu layer thicknesses. The results show that the Cu/Ti/Al contact forms ohmic contact with a contact resistivity of 1.0×10-4 Ω·cm2 after annealing at 800 degrees C. The surface roughness and number of pits on the sample surface increase with the increase of annealing temperature.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Physics, Applied
V. R. Saran Kumar Chaganti, Prafful Golani, Tristan K. Truttmann, Fengdeng Liu, Bharat Jalan, Steven J. Koester
Summary: This study investigated the metal contact resistance of Nd-doped n-type SrSnO3 films, finding significant differences in conductivity among different contact layers. The Ti contact showed the best Ohmic behavior after Al2O3 passivation, with the lowest specific contact resistivity. Temperature-dependent analysis was used to extract barrier height and doping effects for annealed Ti contacts, indicating their potential for high-performance and transparent electronic applications.
APPLIED PHYSICS LETTERS
(2021)
Article
Engineering, Electrical & Electronic
Clement Berger, Daniel Alquier, Micka Bah, Jean-Francois Michaud
Summary: This study focuses on obtaining good ohmic contact using laser annealing on a deposited titanium layer. The results show that with proper laser annealing conditions, contacts with good conductivity can be achieved, and the performance is better than previous studies using titanium laser annealing.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2022)
Article
Physics, Applied
F. Massabuau, D. Nicol, F. Adams, J. Jarman, J. Roberts, A. Kovacs, P. Chalker, R. Oliver
Summary: This study investigates the electrical, structural, and chemical properties of Ti contacts on atomic layer deposited alpha-Ga2O3 films. It demonstrates that the contact performance is strongly influenced by annealing temperature, and the electrical improvement or degradation can be attributed to oxidation of the Ti metallic layer by the Ga2O3 film and Ti diffusion into the Au layer. It emphasizes the importance of phase-specific and growth method-specific studies on contacts for Ga2O3 devices.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Crystallography
Niannian Ge, Caiping Wan, Zhi Jin, Hengyu Xu
Summary: This paper investigates the influence of Ti and W on the electrical and structural properties of Ni-based ohmic contacts to n-type 4H-SiC. It is found that the specific contact resistances (SCRs) vary with different contact structures due to the proportion of contact area occupied by different crystal planes at the interface. The incorporation of the W layer reduces SCR by contributing to a higher relative proportion, while the Ti layer increases SCR due to the incorporation of metal oxides and carbides. The discovery provides valuable insights into tuning surface morphology for wire bonding.
JOURNAL OF CRYSTAL GROWTH
(2023)
Article
Nanoscience & Nanotechnology
Taoufik Slimani Tlemcani, Clement Mauduit, Micka Bah, Meiling Zhang, Matthew Charles, Romain Gwoziecki, Arnaud Yvon, Daniel Alquier
Summary: This study investigates the formation of Au-free Ohmic contacts on p-type GaN using a bilayer Ni/Al-doped ZnO (AZO) thin film. The results show that the contact resistance can be significantly reduced using a suitable thermal process, reaching the lowest value of 1.85 x 10-4 ohm·cm2 for a sample with a 5 nm Ni layer annealed at 500 degrees C in air for 5 min.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Chemistry, Multidisciplinary
Ming-Hsun Lee, Ta-Shun Chou, S. Bin Anooz, Zbigniew Galazka, Andreas Popp, Rebecca L. Peterson
Summary: In this study, the anisotropic nature of monoclinic Ga2O3 was utilized to improve Ti/Au ohmic contact performance. The findings suggest that the dominant charge transport mechanism across the Ti/Au-Ga2O3 junction depends on whether reactive ion etching was used prior to metallization.
Article
Physics, Applied
Nan Jin, Yugang Zhou, Yan Guo, Sai Pan, Rong Zhang, Youdou Zheng
Summary: This work presents the fabrication and analysis of high-reflectivity Ag nanodot (AgND)/Mg/Al Ohmic contacts on both p-GaN and n-GaN. The contacts showed low specific resistance and excellent thermal stability. X-ray photoelectron spectroscopy and x-ray diffraction measurements were conducted to investigate the contact mechanisms. The results suggest that this contact scheme can improve the density of GaN-based ICs and micro-LEDs, as well as enhance the light output efficiency of GaN-based LEDs.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Engineering, Electrical & Electronic
Ahmad Echresh, Slawomir Prucnal, Zichao Li, Rene Huebner, Fabian Ganss, Oliver Steuer, Florian Baerwolf, Shima Jazavandi Ghamsari, Manfred Helm, Shengqiang Zhou, Artur Erbe, Lars Rebohle, Yordan M. Georgiev
Summary: Accurate control of doping and fabrication of metal contacts on n-type germanium nanowires (GeNWs) remain challenging in germanium-based nanoelectronics. This study presents a combined approach involving phosphorus implantation, flash lamp annealing, electron beam lithography, reactive ion etching, and nickel deposition to fabricate Ohmic contacts on n-type doped GeNWs. The resulting devices showed linear Ohmic behavior in current-voltage measurements, and the electrical characteristics were found to be affected by carrier scattering and reduction of the effective NW cross-section.
ACS APPLIED ELECTRONIC MATERIALS
(2022)
Article
Engineering, Electrical & Electronic
Sheng Gao, Xiaoyi Liu, Jingxiong Chen, Zijing Xie, Quanbin Zhou, Hong Wang
Summary: In this study, Ti/Al/Ni/Ti metal stack was proposed to enhance the breakdown voltage of GaN-based HEMTs. The use of magnetron sputtering technique ensured better particle filling on the sidewall, resulting in a more uniform electric-field distribution near the ohmic contacts even after high temperature annealing. Compared to Ti/Al/Ni/Au ohmic contacts, HEMTs with Ti/Al/Ni/Ti ohmic contacts exhibited higher breakdown voltage and improved uniformity and repeatability.
IEEE ELECTRON DEVICE LETTERS
(2021)
Review
Physics, Applied
Chao Lu, Xueqiang Ji, Zeng Liu, Xu Yan, Nianpeng Lu, Peigang Li, Weihua Tang
Summary: This review summarizes recent research progress on beta-Ga2O3-metal contacts, including related theories, measurements, fabrication processes, and control methods. These studies provide important insights for both theoretical understanding of the metal/semiconductor interface and the fabrication process for engineering applications of Ga2O3-based devices.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
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
Optics
Hooman Barati Sedeh, Danilo G. Pires, Nitish Chandra, Jiannan Gao, Dmitrii Tsvetkov, Pavel Terekhov, Ivan Kravchenko, Natalia Litchinitser
Summary: Structured lights, such as beams with spin and orbital angular momenta and various polarizations, have attracted interest for their unique properties in optical and quantum communications, micromanipulation, and imaging. Additionally, structured optical materials have opened new opportunities for controlling light flow and sensing. However, the interaction between structured light and complex-shaped materials has not been fully explored.
LASER & PHOTONICS REVIEWS
(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
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
Engineering, Electrical & Electronic
Yuan Qin, Ming Xiao, Ruizhe Zhang, Qingyun Xie, Tomas Palacios, Boyan Wang, Yunwei Ma, Ivan Kravchenko, Dayrl P. Briggs, Dale K. Hensley, Bernadeta R. Srijanto, Yuhao Zhang
Summary: This work presents the fabrication of quasi-vertical GaN Schottky barrier diodes (SBDs) on a 6-inch Si substrate with a record-breaking breakdown voltage (BV) of over 1 kV. The novel use of a deep mesa in quasi-vertical devices allows for a self-aligned edge termination, and the mesa sidewall is covered by p-type nickel oxide (NiO) to reduce the surface field. The device exhibits a parallel-plane junction electric field of 2.8 MV/cm, along with low turn-on voltage and specific on-resistance. Additionally, it demonstrates excellent overvoltage robustness under continuous stress.
IEEE ELECTRON DEVICE LETTERS
(2023)
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)
