Article
Chemistry, Physical
Adam Szyszka, Mateusz Wosko, Regina Paszkiewicz
Summary: This article proposes a new methodology that combines various microscopy techniques to characterize the electrical properties of AlGaN/GaN/Si heterostructures at the nanoscale, and investigates the influence of different surface defects on the local electrical properties. The study reveals insights into the formation of 2DEG at the AlGaN/GaN interface and the impact of surface defects on electron transport properties, shedding light on the origins of long relaxation time effects in AlGaN/GaN heterostructures.
APPLIED SURFACE SCIENCE
(2021)
Article
Optics
Sergi Cuesta, Yoann Cure, Fabrice Donatini, Lou Denaix, Edith Bellet-Amalric, Catherine Bougerol, Vincent Grenier, Quang-Minh Thai, Gilles Nogues, Stephen T. Purcell, Le Si Dang, Eva Monroy
Summary: This study investigates the impact of spontaneous and piezoelectric polarization on carrier diffusion in undoped AlGaN/GaN separate confinement heterostructures. Carrier collection is greatly enhanced with the use of an asymmetric graded-index separate confinement heterostructure (GRINSCH), which helps reduce potential barriers induced by polarization differences and improves the overall performance of the electron pumped ultraviolet lasers.
Article
Materials Science, Multidisciplinary
Rong Wang, Jianxing Xu, Shiyong Zhang, Ying Zhang, Penghui Zheng, Zhe Cheng, Lian Zhang, Feng-Xiang Chen, Xiaodong Tong, Yun Zhang, Wei Tan
Summary: Low-fluence neutron irradiation is a promising way to reduce the reverse leakage current in AlGaN/GaN heterostructures while maintaining other electronic properties almost unchanged. The mechanism involves the mobility of neutron scattered group-III interstitials, passivation of V-III-DLs, and escape of interstitials after saturation of passivation. This post-processing treatment offers a new approach for improving the electronic properties of AlGaN/GaN heterostructures grown by MOCVD on sapphire substrates.
JOURNAL OF MATERIALS CHEMISTRY C
(2021)
Article
Physics, Applied
Hao Yu, Vamsi Putcha, Uthayasankaran Peralagu, Ming Zhao, Sachin Yadav, Alireza Alian, Bertrand Parvais, Nadine Collaert
Summary: This study provides a comprehensive analysis of the leakage current mechanism in ion implantation isolation (I/I/I) regions of GaN high electron mobility transistors. The analysis reveals a positive correlation between the activation energy of R-sh and the energy level of the leakage path, and constructs the energy band diagram of the isolation region. A novel method to estimate the net active defect density caused by I/I/I is proposed, extracting net active defect densities in the GaN and AlGaN layers.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Chemistry, Physical
Dmitri S. S. Arteev, Alexei V. V. Sakharov, Wsevolod V. V. Lundin, Evgenii E. E. Zavarin, Andrey E. E. Nikolaev, Andrey F. F. Tsatsulnikov, Viktor M. M. Ustinov
Summary: This study investigates the influence of Fe segregation on the electrical properties of two-dimensional electron gas in AlGaN/AlN/GaN heterostructures. It was found that the concentration and mobility of the electron gas decrease with thinner channel layer thickness, leading to an increase in sheet resistance. The drop in mobility is attributed to a combination of ionized impurity scattering and various scattering effects.
Article
Materials Science, Multidisciplinary
Kavita T. Upadhyay, Manju K. Chattopadhyay
Summary: This paper provides a review of significant research work in the field of GaN-based sensor technologies, including classification of existing work, explanation of sensor sensing mechanisms, as well as the challenges and future opportunities facing current sensing systems.
MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Roman B. Adamov, Daniil Pashnev, Vadim A. Shalygin, Maria D. Moldavskaya, Maxim Ya. Vinnichenko, Vytautas Janonis, Justinas Jorudas, Saulius Tumenas, Pawel Prystawko, Marcin Krysko, Maciej Sakowicz, Irmantas Kasalynas
Summary: Terahertz time-domain spectroscopy and Fourier-transform infrared spectroscopy were used to investigate the high-frequency characteristics of two-dimensional electron gas and GaN:C buffer layers in AlGaN/AlN/GaN heterostructures. Results showed good agreement between experiment and theory, revealing the temperature dependent electron effective mass and small damping factors of optical phonons due to high crystal quality of epitaxial layers on the SiC substrate.
APPLIED SCIENCES-BASEL
(2021)
Article
Materials Science, Multidisciplinary
Xiao Cui, Keyu Ji, Taiping Zhang, Bingjun Wang, Wei Sha, Zilong Dong, Yuanhong Shi, Chunsheng Jiang, Qilin Hua, Weiguo Hu
Summary: This paper investigates the influence of low-fluence neutron irradiation on the electrical properties of AlGaN/GaN HEMTs. The results show that the output performance of the irradiated samples changes similarly, with almost no changes or slight decreases near the knee voltage. As for the leakage current, samples irradiated with different fluences exhibit different characteristics. Simulations using Crosslight software further reveal that low-fluence neutron irradiation primarily affects the 2DEG mobility and surface states of the HEMTs.
ADVANCED MATERIALS TECHNOLOGIES
(2023)
Article
Crystallography
Daqing Peng, Zhonghui Li, Chuanhao Li, Qiankun Yang, Dongguo Zhang, Weike Luo, Xun Dong
Summary: AlGaN/GaN heterojunction with AlGaN buffer was grown on 6-inch semi-insulating SiC substrate using MOCVD. The structures of GaN/AlGaN compound buffer and pure AlGaN buffer effectively reduced the tensile stress caused by mismatch with SiC substrate compared to GaN buffer. The relationship between stress and AlGaN buffer thickness was analyzed, and the crystal quality of AlGaN buffer was improved by increasing AlN nucleation growth temperature. High-quality and low-stress AlGaN/GaN heterojunction with AlGaN buffer grown on 6-inch semi-insulating SiC substrate was obtained.
JOURNAL OF CRYSTAL GROWTH
(2023)
Article
Nanoscience & Nanotechnology
Eric N. Jin, Brian P. Downey, Vikrant J. Gokhale, Jason A. Roussos, Matthew T. Hardy, Tyler A. Growden, Neeraj Nepal, D. Scott Katzer, Jeffrey P. Calame, David J. Meyer
Summary: The epitaxial integration of high dielectric constant Sr1-xCaxTiO3 films onto AlGaN/GaN/4H-SiC structures has shown promising results in improving electric field management and device breakdown voltage without significant impact on channel transport properties. The films exhibit minimal hysteresis, high dielectric constant, and reduced leakage compared to Schottky contacted samples, indicating their potential for enhancing functionality and performance in high-power RF and power-switching applications.
Article
Chemistry, Physical
Patrick Fiorenza, Emanuela Schiliro, Giuseppe Greco, Marilena Vivona, Marco Cannas, Filippo Giannazzo, Raffaella Lo Nigro, Fabrizio Roccaforte
Summary: The study investigates charge trapping phenomena in Al2O3 thin films grown on AlGaN/GaN heterostructures by ALD, using time-dependent C-V measurements. Results show competitive mechanisms for electron capture and emission in the Al2O3 film, as well as the presence of oxygen-related point defects with only a fraction being electrically active. These findings are valuable for understanding the thermal stability of trapping phenomena and potential applications in real devices.
APPLIED SURFACE SCIENCE
(2022)
Article
Physics, Condensed Matter
X. J. Zhou, D. Lei, K. N. M. L. Men, Y. Xing
Summary: Using the dielectric continuous model and transfer matrix method, the confined and propagating optical phonon modes in AlGaN/GaN double-channel heterostructures were studied, revealing two groups of low-and high-frequency modes influenced by thickness and composition.
SUPERLATTICES AND MICROSTRUCTURES
(2021)
Article
Engineering, Electrical & Electronic
Akhil Ranjan, Ravikiran Lingaparthi, Nethaji Dharmarasu, K. Radhakrishnan
Summary: This study establishes a theoretical relationship between the properties of a two-dimensional electron gas (2DEG) in AlGaN/GaN HEMT heterostructure and various gas-sensing characteristics. It is proposed that using a thinner barrier layer in the heterostructure can lead to lower detection limits, higher sensing response, and faster response time. Experimental results confirm these analytical findings by comparing a thin-barrier gas sensor with a thick-barrier gas sensor.
IEEE SENSORS JOURNAL
(2022)
Article
Chemistry, Multidisciplinary
Chenguang Zhang, Wenliang Wang, Xiaodong Hao, Yong Peng, Yulin Zheng, Jia Liu, Yiyuan Kang, Fujian Zhao, Zhengtang Luo, Junjie Guo, Bingshe Xu, Longquan Shao, Guoqiang Li
Summary: This study utilized GaN/AlGaN materials with controlled polarity to induce endogenous electrical stimulation for bone regeneration, finding that Ga-polarity GaN/AlGaN nanofilms showed superior bone repair in vivo and promoted osteogenic differentiation of bone mesenchymal stem cells in vitro. Additionally, the study revealed that bone morphogenetic protein-6 (BMP6) may be an electrically sensitive osteogenic protein.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Engineering, Electrical & Electronic
Feiyuan Yang, Manikant Singh, Michael J. Uren, Trevor Martin, Hassan Hirshy, Michael A. Casbon, Paul J. Tasker, Martin Kuball
Summary: The breakdown mechanism in 0.25-μm gate length AlGaN/GaN-on-SiC transistors is investigated using the drain current injection technique. The results show that breakdown can be divided into two stages, which are related to gate voltage levels and material characteristics.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Chemistry, Physical
J. More-Chevalier, S. Cichon, L. Horak, J. Bulik, P. Hubik, Z. Gedeonova, L. Fekete, M. Poupon, J. Lancok
APPLIED SURFACE SCIENCE
(2020)
Article
Crystallography
T. Hubacek, A. Hospodkova, K. Kuldova, M. Slavicka Zikova, J. Pangrac, J. Cizek, M. O. Liedke, M. Butterilng, A. Wagner, P. Hubik, E. Hulicius
JOURNAL OF CRYSTAL GROWTH
(2020)
Article
Materials Science, Multidisciplinary
Lucie Prusakova, Pavel Hubik, Asim Aijaz, Tomas Nyberg, Tomas Kubart
Article
Nanoscience & Nanotechnology
Marie Krecmarova, Michal Gulka, Thijs Vandenryt, Jaroslav Hruby, Ladislav Fekete, Pavel Hubik, Andrew Taylor, Vincent Mortet, Ronald Thoelen, Emilie Bourgeois, Milos Nesladek
Summary: The label-free biosensor concept is based on manipulation of charge state of nitrogen-vacancy (NV) quantum color centers in diamond, combined with an electrochemical microfluidic flow cell sensor. The functionality of the device was demonstrated by optical detection of DNA molecules, using a strongly cationic charged polymer to shift the charge state of NV centers. The developed electrochemical device can also be applied to nuclear magnetic resonance spin sensing.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Review
Physics, Multidisciplinary
Jiri J. Mares, Vaclav Spicka, Pavel Hubik
Summary: This paper analyzes the role of extracellular tissue in signal transfer and information processing in biological neural networks, proposing that the diffusion of action potential and polarization waves in surrounding ECT control fundamental parameters. It suggests that ephaptic coupling between neighboring neurons is responsible for information processing, which challenges current models of neural networks.
EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS
(2021)
Article
Engineering, Electrical & Electronic
Frantisek Hajek, Alice Hospodkova, Pavel Hubik, Zuzana Gedeonova, Tomas Hubacek, Jiri Pangrac, Karla Kuldova
Summary: This study investigates the influence of dislocation density on the transport properties of HEMT structures, demonstrating that reducing the dislocation density can significantly enhance electron mobility in 2DEG and improve the performance of high-frequency GaN HEMT applications.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2021)
Article
Materials Science, Multidisciplinary
Jiri Bulir, Joris More-Chevalier, Sergii Chertopalov, Ladislav Fekete, Lenka Volfova, Pavel Hubik, Michal Novotny, Jan Lancok
Summary: This work investigates the electron-transport behavior and mechanism of zirconium nitride films prepared by RF magnetron sputtering using a Zr target in reactive nitrogen ambient. The electron transport properties were estimated at each stage of the deposition process by analyzing the model parameters, and the thickness-dependent phenomenon was discussed.
Article
Materials Science, Multidisciplinary
Nicolas Lambert, Zdenek Weiss, Ladislav Klimsa, Jaromir Kopecek, Zuzana Gedeonova, Pavel Hubik, Vincent Mortet
Summary: In this work, phosphorus-doped polycrystalline diamond layers were grown using a new gas control process, and their topographical characteristics and crystalline quality were analyzed. The layers exhibited good crystalline quality with a high growth rate and phosphorus concentration.
DIAMOND AND RELATED MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
P. Hazdra, A. Laposa, Z. Soban, A. Taylor, N. Lambert, V. Povolny, J. Kroutil, Z. Gedeonov, P. Hubik, V. Mortet
Summary: Pseudo-vertical diodes on {113} oriented homoepitaxial boron-doped diamond were fabricated using molybdenum as both the Schottky and ohmic contacts. The results show that these diodes have good current characteristics and stability at high temperatures. This technology is of great significance for the fabrication of high-temperature power devices.
DIAMOND AND RELATED MATERIALS
(2022)
Article
Crystallography
T. Hubacek, K. Kuldova, Z. Gedeonova, F. Hajek, T. Kosutova, S. Banerjee, P. Hubik, J. Pangrac, T. Vanek, A. Hospodkova
Summary: The impact of Ge doping on InGaN layers grown with the Metal Organic Vapor Phase Epitaxy technique was investigated, focusing on the influence of GeH4 flow and Ga/III ratio on the luminescence, electrical, and structural properties of InGaN:Ge layers. It was found that at doping levels above 1019 cm-3, an increase in GeH4 flow resulted in a decrease in the In content and lower concentration of free carrier density in InGaN layers. However, the change in Ga/III ratio did not affect the luminescence and structural properties. The unintentional Ge doping of InGaN layers due to the Ge memory effect or back diffusion was also discussed.
JOURNAL OF CRYSTAL GROWTH
(2023)
Article
Materials Science, Multidisciplinary
Andrew Taylor, Petr Ashcheulov, Pavel Hubik, Zdenek Weiss, Ladislav Klimsa, Jaromir Kopecek, Jan Hrabovsky, Martin Veis, Jan Lorincik, Ivan Elantyev, Vincent Mortet
Summary: This study compared the values of total boron content and hole carrier concentration obtained from different destructive and non-destructive quantification methods in boron doped nano-crystalline diamond films. Destructive secondary-ion mass spectrometry and relatively unreported glow discharge optical emission spectrometry were used, along with non-destructive Raman, spectroscopic ellipsometry, and van der Pauw Hall measurements. The measurement techniques and their details were discussed, and the measured values were compared and discussed in terms of their viability for estimating total boron and electrically active boron in doped nano-crystalline diamond layers.
DIAMOND AND RELATED MATERIALS
(2023)
Article
Crystallography
Alice Hospodkova, Frantisek Hajek, Tomas Hubacek, Zuzana Gedeonova, Pavel Hubik, Jirf J. Mares, Jirf Pangrac, Filip Dominec, Karla Kuldova, Eduard Hulicius
Summary: Although various aspects of GaN high electron mobility transistor (HEMT) structure have been extensively studied, such as buffer layer architecture, AlGaN barrier, surface passivation, and dielectric choice, little attention has been given to optimize the GaN channel technology. In this work, we demonstrate that by optimizing the channel technology, electron mobility can be significantly improved. We investigated the influence of technological parameters on the transport properties of a series of GaN layers mimicking a HEMT channel. We focused on the layer growth using TEG precursor and examined parameters such as reactor atmosphere, growth temperature, growth rate influenced by precursor concentration, and reactor pressure. By using optimized growth parameters for the HEMT structure, we successfully increased the electron mobility in 2DEG by 30%.
JOURNAL OF CRYSTAL GROWTH
(2023)
Proceedings Paper
Engineering, Electrical & Electronic
F. Dubecky, P. Hubik, G. Vanko, B. Zat'ko, P. Bohacek, M. Sekacova, A. Sagatova, V Necas
2020 13TH INTERNATIONAL CONFERENCE ON ADVANCED SEMICONDUCTOR DEVICES AND MICROSYSTEMS (ASDAM 2020)
(2020)
Article
Materials Science, Multidisciplinary
N. Lambert, A. Taylor, P. Hubik, J. Bulir, J. More-Chevalier, H. Karaca, C. Fleury, J. Voves, Z. Soban, D. Pogany, V Mortet
DIAMOND AND RELATED MATERIALS
(2020)