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
Physics, Applied
O. Ambacher, B. Christian, M. Yassine, M. Baeumler, S. Leone, R. Quay
Summary: The electrical properties of pseudomorphic MeAl1-xN/GaN, MeAl1-xN/AlN, and MeAl1-xN/InN heterostructures and devices are significantly influenced by the piezoelectric and spontaneous polarization of wurtzite ScxAl1-xN, GaxAl1-xN, and InxAl1-xN ternary compounds. Predictions of polarization-induced interface charges and comparisons of different heterostructures suggest superior potential in ScAlN/GaN-based structures for high electron mobility transistors in high-frequency and power electronic applications.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Engineering, Electrical & Electronic
Junya Yaita, Koichi Fukuda, Atsushi Yamada, Takuya Iwasaki, Shu Nakaharai, Junji Kotani
Summary: The study identified the primary reason for the reduced electron mobility in QW GaN-HEMT and proposed a solution to alleviate the electric field and increase electron mobility. As a result, the electron mobility of the QW GaN-HEMT structure was significantly improved.
IEEE ELECTRON DEVICE LETTERS
(2021)
Article
Computer Science, Information Systems
Mohammad Abdul Alim, Abu Zahed Chowdhury, Shariful Islam, Christophe Gaquiere, Giovanni Crupi
Summary: This paper provides a comparative analysis of the thermal impact on the microwave performance of high electron-mobility transistors (HEMTs) based on GaAs and GaN technologies, showing that while similar trends are observed for the two different technologies, the impact of temperature is more pronounced in the GaN device.
Article
Engineering, Electrical & Electronic
Huaxing Jiang, Renqiang Zhu, Qifeng Lyu, Chak Wah Tang, Kei May Lau
Summary: This paper presents recent research on normally-OFF operation and high-performance device merits in GaN HEMTs, enabled by thin-barrier AlGaN/GaN heterostructures. Investigating two types of thin-barrier HEMTs with MOS gate and p-GaN gate stack structures, the study discusses the benefits and tradeoffs of thin-barrier MOSHEMTs and p-GaN gate HEMTs.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2021)
Article
Chemistry, Multidisciplinary
M. Bikerouin, O. Chdil, M. Balli
Summary: Janus monolayers, achieved by breaking the vertical structural symmetry of 2D materials, hold great promise for high-quality and high-performance atomically-thin vertical p-n heterojunction solar cells. By employing first-principles computations, Janus group-III chalcogenide monolayers are investigated for their potential use in 2D photovoltaic systems, revealing their optimal band gap, high charge carrier mobilities, and strong light absorption. Analysis of band alignments identifies 46 type-II van der Waals heterostructures with a lattice mismatch of less than 5%, including 7 vertical heterojunctions with a power conversion efficiency higher than 20%. These findings suggest that Janus monolayers and van der Waals heterostructures could serve as materials for next-generation optoelectronic and photovoltaic devices.
Article
Engineering, Electrical & Electronic
Christian Manz, Stefano Leone, Lutz Kirste, Jana Ligl, Kathrin Frei, Theodor Fuchs, Mario Prescher, Patrick Waltereit, Marcel A. Verheijen, Andreas Graff, Michel Simon-Najasek, Frank Altmann, Michael Fiederle, Oliver Ambacher
Summary: AlScN/GaN epitaxial heterostructures have shown great potential for high-frequency and high-power electronic applications, with promising device performance. The AlScN/GaN heterostructures processed by MOCVD method exhibit improved structural quality.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2021)
Article
Physics, Applied
Pengfei Shao, Xing Fan, Siqi Li, Songlin Chen, Hui Zhou, Huan Liu, Hui Guo, Weizong Xu, Tao Tao, Zili Xie, Hong Lu, Ke Wang, Bin Liu, Dunjun Chen, Youdou Zheng, Rong Zhang
Summary: We have investigated the 2DHGs in GaN/AlGaN/GaN heterostructures and achieved the highest recorded 2DHG sheet density and conductivity on this platform. The results show that the 2DHG density increases significantly with increasing Al composition in the AlGaN barriers, making it beneficial for the fabrication of p-channel GaN transistors with lower on-resistance.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Can Zou, Zixuan Zhao, Mingjun Xu, Xingfu Wang, Qing Liu, Kai Chen, Longfei He, Fangliang Gao, Shuti Li
Summary: To address the issue of minority carrier storage time in bipolar transistors, a hot electron transistor (HET) has been proposed. This device offers high working speed and the ability to perform complex logic functions with just one component. A mixed-dimensional HET composed of GaN/AlN microwires, graphene (Gr), and Si has been demonstrated, which achieves high speed hot electrons by injecting electrons between GaN/AlN into graphene through F-N tunneling mechanism, allowing for ballistic transport and collection through low-barrier Si. The device exhibits a record DC gain of 16.2, collection efficiency close to the limit of 99.9% based on GHET, emitter current density of 68.7 A/cm2, high on/off current ratio of approximately 107, and wide current saturation range, making it suitable for potential applications as a power amplifier.
Article
Engineering, Electrical & Electronic
Marek Wzorek, Marek Ekielski, Jaroslaw Tarenko, Michal A. Borysiewicz, Ernest Brzozowski, Andrzej Taube
Summary: The thermal stability of Schottky contacts to AlGaN/GaN heterostructures was evaluated by subjecting them to high-temperature annealing. Cu/ and Au/Ni/ contacts showed changes in electrical properties after annealing, while Cu/Pd2Si/ contacts remained stable.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Engineering, Electrical & Electronic
Junao Cheng, Mohammad Wahidur Rahman, Andy Xie, Hao Xue, Shahadat Hasan Sohel, Edward Beam, Cathy Lee, Hao Yang, Caiyu Wang, Yu Cao, Siddharth Rajan, Wu Lu
Summary: In this study, ScAlN/GaN dielectric superjunction high-electron-mobility transistors with high-k passivation layer BZN were demonstrated to enhance breakdown voltage. The use of SiN/BZN/SiN sandwiched passivation layer improved the average breakdown voltage while maintaining similar fT and fmax values. This work shows that high current and high breakdown voltage can be achieved simultaneously on semiconductor heterostructures with high sheet charge density by integrating high-k dielectrics.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2021)
Article
Engineering, Electrical & Electronic
Yuji Ando, Ryutaro Makisako, Hidemasa Takahashi, Akio Wakejima, Jun Suda
Summary: The study revealed that the epitaxial layer structure affects the electrical characteristics of AlGaN/GaN HEMTs. GaN-on-GaN HEMTs showed an improved tradeoff between maximum drain current and breakdown characteristics compared to GaN-on-SiC HEMTs. Moreover, the impact of Fe diffusion on frequency dispersion was relatively limited in GaN-on-GaN devices.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Physics, Applied
S. Zoino, L. Borowik, B. Mohamad, E. Nowak, P. Kempisty
Summary: The formation of a two-dimensional electron gas (2DEG) at the GaN (0001)/AlN interface holds significant implications for GaN-based high-voltage and high-frequency (RF) devices. Recent ab initio simulations shed light on the role of polarizations in driving the formation of the 2DEG, and the study also investigates the impact of fixed charges and additional layers on the carrier concentration.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Zexuan Zhang, Jimy Encomendero, Eungkyun Kim, Jashan Singhal, YongJin Cho, Kazuki Nomoto, Masato Toita, Huili Grace Xing, Debdeep Jena
Summary: The study revealed the presence of high-density 2D electron gas in Al(Ga)N/GaN heterojunctions, and achieved low sheet resistance in N-polar undoped pseudomorphic GaN/AlGaN structures. These results provide important insights for the development of high-power RF electronics based on N-polar III-nitride high electron mobility transistors.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Xiaoyue Zhang, Ning Tang, Liuyun Yang, Chi Fang, Caihua Wan, Xingchen Liu, Shixiong Zhang, Yunfan Zhang, Xinqiang Wang, Yuan Lu, Weikun Ge, Xiufeng Han, Bo Shen
Summary: The spin injection into 2D electron gas in AlN/GaN heterostructures was studied, showing long spin relaxation time and the mechanism of spin injection. The results reveal the promising potential of 2DEG in AlN/GaN heterostructures for spin field-effect transistor applications.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Chemistry, Applied
Nicoleta G. Apostol, Marius A. Husanu, Daniel Lizzit, Ioana A. Hristea, Cristina F. Chirila, Lucian Trupina, Cristian M. Teodorescu
Summary: The experiment investigates carbon monoxide adsorption and desorption on gold deposited on ferroelectric lead zirco-titanate, revealing the negative charge state of gold and the formation of gold nanoparticles. The neutral carbon adsorption is closely related to the polarization of the ferroelectric film, while carbon in molecular form is related to its bonding on metal nanoparticles. Desorbed carbon at higher temperature uptakes oxygen from the substrate.
Article
Chemistry, Multidisciplinary
Alla Chikina, Dennis Christensen, Vladislav Borisov, Marius-Adrian Husanu, Yunzhong Chen, Xiaoqiang Wang, Thorsten Schmitt, Milan Radovic, Naoto Nagaosa, Andrey S. Mishchenko, Roser Valenti, Nini Pryds, Vladimir N. Strocov
Summary: The rich functionalities of transition-metal oxides and their interfaces have great technological potential, with recent research showing a significant boost in electron mobility at certain oxide interfaces. Understanding the fundamental physics behind these mobility enhancements, such as through band-order engineering and symmetry properties, can lead to improved performance of oxide devices.
Article
Materials Science, Multidisciplinary
Cristina Chirila, Georgia Andra Boni, Lucian Dragos Filip, Marius Husanu, Stefan Neatu, Cosmin Marian Istrate, Gwenael Le Rhun, Bertrand Vilquin, Lucian Trupina, Iuliana Pasuk, Mihaela Botea, Ioana Pintilie, Lucian Pintilie
Summary: The study revealed that PZT films grown on Si substrates exhibit different polarization and dielectric constant, along with a larger value for the pyroelectric coefficient, which are influenced by the structural quality and stoichiometry of the films.
MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS
(2021)
Article
Chemistry, Physical
V. N. Strocov, F. Lechermann, A. Chikina, F. Alarab, L. L. Lev, V. A. Rogalev, T. Schmitt, M-a Husanu
Summary: The electronic structure of LaAlO3/SrTiO3 (LAO/STO) samples was investigated by soft-x-ray ARPES, revealing a 3D behavior of the x-ray generated mobile electron system (MES).
ELECTRONIC STRUCTURE
(2022)
Article
Chemistry, Multidisciplinary
Hang Li, Yulin Gan, Marius-Adrian Husanu, Rasmus Tindal Dahm, Dennis Valbjorn Christensen, Milan Radovic, Jirong Sun, Ming Shi, Baogen Shen, Nini Pryds, Yunzhong Chen
Summary: This study investigates the metallic band dispersion at the LaAlO3/SrTiO3 heterointerface using soft X-ray angle-resolved photoemission spectroscopy. The results show that the insertion of a LaMnO3 buffer layer not only enhances the electron mobility, but also makes the electronic structure robust against X-ray radiation. Moreover, the buffer layer strongly suppresses the formation of oxygen vacancies and the electron-phonon interaction on the SrTiO3 side.
Article
Physics, Applied
S. Shavkin, V. V. Guryev, N. K. Chumakov, A. Irodova, V. S. Kruglov
Summary: Magnetization curves of narrow rectangular samples from superconducting Nb-Ti cold-rolled tape were measured using a Vibrating-Sample Magnetometer (VSM). Two types of samples, sliced along and across the rolling direction, were analyzed. An anomalous shift of the magnetization central peak was observed only in the samples sliced across the rolling direction, which is opposite to the usual shift observed in bulk materials. Magneto-Optical Imaging (MOI) pictures provide a possible mechanism for this anomalous shift, showing a dendritic structure of magnetic flux penetrating from the transverse side of the sample.
JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM
(2022)
Article
Geochemistry & Geophysics
Cristian M. Teodorescu, Marius A. Husanu
Summary: A recent theory suggests the possibility of 're-entrant' ferromagnetism in 3d metals at temperatures far above their boiling points. This study investigates the hypothesis of the Earth's inner solid core becoming ferromagnetic and finds that the hexagonal close-packed structure is responsible for the geomagnetic field. The findings also suggest that the reversal of the magnetic field may be achieved through simple rotation of the magnetization of the core, which could have beneficial effects for complex lifeforms and human civilization.
PHYSICS OF THE EARTH AND PLANETARY INTERIORS
(2022)
Article
Materials Science, Multidisciplinary
M. Y. Chernykh, A. A. Andreev, I. S. Ezubchenko, I. A. Chernykh, I. O. Mayboroda, E. M. Kolobkova, J. Grishchenko, P. A. Perminov, V. S. Sedov, A. K. Martyanov, A. S. Altakhov, M. S. Komlenok, V. P. Pashinin, A. G. Sinogeykin, V. Konov, M. L. Zanaveskin
Summary: A new approach to fabricating efficient heat sinks for GaN-based transistors is demonstrated, which involves growing a polycrystalline diamond coating on the functional silicon layer of SOI wafers and etching a thick silicon substrate and thin thermal oxide. The heat sink, consisting of a thin monocrystalline silicon layer on top of a thick polycrystalline diamond layer, shows improved heat removal performance compared to conventional technologies. This new substrate fabrication technology has a positive impact on GaN-based device output characteristics and reliability, benefiting communication systems, radars, and secondary power supply systems.
APPLIED MATERIALS TODAY
(2022)
Article
Physics, Multidisciplinary
Marius Adrian Husanu, Dana Georgeta Popescu, Federico Bisti, Luminita Mirela Hrib, Lucian Dragos Filip, Iuliana Pasuk, Raluca Negrea, Marian Cosmin Istrate, Leonid Lev, Thorsten Schmitt, Lucian Pintilie, Andrey Mishchenko, Cristian Mihail Teodorescu, Vladimir N. Strocov
Summary: A deeper understanding of the coupling at the interface of multiferroics heterostructures has been achieved through the use of synchrotron radiation techniques. The authors used k-resolved soft X-ray photoemission spectroscopy and first principles calculations to investigate the band structure of several multiferroic heterostructures, identifying the distinct signature of the interface. The experimental results revealed the influence of ferroelectric polarization on charge density, electron-lattice interaction, and mobility of charge carriers in these systems.
COMMUNICATIONS PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Dana Georgeta Popescu, Marius Adrian Husanu, Procopios Christou Constantinou, Lucian Dragos Filip, Lucian Trupina, Cristina Ioana Bucur, Iuliana Pasuk, Cristina Chirila, Luminita Mirela Hrib, Viorica Stancu, Lucian Pintilie, Thorsten Schmitt, Cristian Mihail Teodorescu, Vladimir N. Strocov
Summary: The intrinsic band structure and polarization dependent electrostatic potential profile of Pb(Zr0.2Ti0.8)O-3 (PZT) material are determined using soft-X-ray angle-resolved photoelectron spectroscopy (ARPES) for the first time. Oxygen vacancies and cation vacancies are identified as the origin of the charge distribution near the PZT film surface.
Article
Chemistry, Multidisciplinary
Laura E. Abramiuc, Liviu C. Tanase, Mauricio J. Prieto, Lucas de Souza Caldas, Aarti Tiwari, Nicoleta G. Apostol, Marius A. Husanu, Cristina F. Chirila, Lucian Trupina, Thomas Schmidt, Lucian Pintilie, Cristian M. Teodorescu
Summary: The free surface ferroelectric properties of thin polar films can be studied by estimating band bending variance or by analyzing the extrinsic charge outside the surface. In this study, the ferroelectric lead zirco-titanate (PZT) is investigated using a combination of low energy/mirror electron microscopy (LEEM/MEM), photoemission electron microscopy (PEEM), and high-resolution photoelectron spectroscopy (XPS). The results show a significant accumulation of extrinsic negative compensation charge on the outward polarized thin film surface, indicating a correlation with the surface electrostatic potential. It is observed that air-exposed high-quality ferroelectric thin films have large negative surface potentials, which are sensitive to beam damage and molecular desorption.
Article
Nanoscience & Nanotechnology
I. S. Ezubchenko, E. M. Kolobkova, A. A. Andreev, M. Ya. Chernykh, Yu. V. Grishchenko, P. A. Perminov, I. A. Chernykh, M. L. Zanaveskin
Summary: Microwave transistors based on AlN/GaN heterostructures on silicon substrates were fabricated and studied. The results showed that these transistors exhibit high specific saturation current, good transconductance, and excellent frequency performance.
NANOBIOTECHNOLOGY REPORTS
(2022)
Article
Physics, Multidisciplinary
L. L. Lev, I. O. Maiboroda, E. S. Grichuk, N. K. Chumakov, N. B. M. Schroeter, M-A Husanu, T. Schmitt, G. Aeppli, M. L. Zanaveskin, V. G. Valeyev, V. N. Strocov
Summary: Band bending at the surface of GaN can be studied using soft-x-ray angle-resolved photoelectron spectroscopy (ARPES). The band bending is found to be upward, reducing the band occupation towards the surface. By quantitatively analyzing the experimental data, a model is proposed to accurately describe the band bending profile and the photoelectron mean free path values.
PHYSICAL REVIEW RESEARCH
(2022)