Article
Physics, Applied
HePeng Zhang, JunShuai Xue, YongRui Fu, LanXing Li, ZhiPeng Sun, JiaJia Yao, Fang Liu, Kai Zhang, XiaoHua Ma, JinCheng Zhang, Yue Hao
Summary: The systematic investigation of AlN/GaN double-barrier resonant tunneling diodes (RTDs) grown on GaN-on-sapphire templates showed promising performance at room temperature, indicating potential for future applications in high-frequency and high-power terahertz radiation. The study revealed key factors affecting device performance, such as the impact of temperature and dislocation density on electrical characteristics.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Nanoscience & Nanotechnology
Remy Vermeersch, Gwenole Jacopin, Florian Castioni, Jean-Luc Rouviere, Alberto Garcia-Cristobal, Ana Cros, Julien Pernot, Bruno Daudin
Summary: The growth and optical properties of GaN quantum disks in AlN nanowires were studied via molecular beam epitaxy to control the emission wavelength of AlN nanowire-based LEDs. In addition to GaN quantum disks with thickness ranging from 1 to 4 monolayers, focus was given to incomplete GaN disks with lateral confinement. Their emission spectrum consists of sharp lines extending down to 215 nm near the AlN band edge. The room temperature cathodoluminescence intensity of GaN quantum disks embedded in AlN nanowires is about 20% of the low temperature value, highlighting the potential of ultrathin/incomplete GaN quantum disks for deep UV emission.
Article
Chemistry, Multidisciplinary
Mario F. Zscherp, Nils Mengel, Detlev M. Hofmann, Vitalii Lider, Badrosadat Ojaghi Dogahe, Celina Becker, Andreas Beyer, Kerstin Volz, Joerg Schoermann, Sangam Chatterjee
Summary: This study successfully optimized the quality of c-GaN epitaxial layers by introducing pre-growth treatments and buffer layers, achieving nearly perfect crystallinity and smooth surfaces and interfaces. The optimized growth parameters resulted in extremely small surface roughness and very limited stacking fault densities in phase pure c-GaN layers. The high structural quality of the epitaxial layers was further confirmed through photoluminescence spectroscopy.
CRYSTAL GROWTH & DESIGN
(2022)
Article
Materials Science, Multidisciplinary
Hao Wu, Xiaojun Fu, Yuan Wang, Jingwei Guo, Jingyu Shen, Shengdong Hu
Summary: The research demonstrates that both the thin GaN buffer and the step-etched GaN structure contribute to improving the breakdown voltage of the AlGaN/GaN HEMT. The optimized structure increases the breakdown voltage to 1487 V while maintaining a low on-state resistance.
RESULTS IN PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
M. Z. Mohd Yusoff, A. Mahyuddin, Z. Hassan, M. S. Yahya
Summary: The study investigates the influence of high thermal annealing on the surface morphological, structural, and optical properties of ZnO/AlN/GaN/AlN layers grown on Si substrate by MBE. ZnO thin film was deposited on AlN/GaN/AlN heterostructures using RF sputtering machine. Thermal annealing at different temperatures (600 degrees C and 800 degrees C) with nitrogen flow was applied to the samples in a vacuum tube furnace. Surface morphological, structural, and optical properties were characterized using FESEM, AFM, HR-XRD, and Raman spectroscopy. The optimal thermal annealing temperature was found to be 600 degrees C, resulting in the lowest dislocation density in the films based on the optical and structural evaluation.
APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING
(2023)
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
Physics, Multidisciplinary
Zhen-Hua Li, Peng-Fei Shao, Gen-Jun Shi, Yao-Zheng Wu, Zheng-Peng Wang, Si-Qi Li, Dong-Qi Zhang, Tao Tao, Qing-Jun Xu, Zi-Li Xie, Jian-Dong Ye, Dun-Jun Chen, Bin Liu, Ke Wang, You-Dou Zheng, Rong Zhang
Summary: A systematic investigation on low growth rate PA-MBE grown GaN was conducted in a wide growth temperature range, identifying the optimal growth temperature window of 700-760 degrees C. The slightly Ga-rich region was preferred for high-quality GaN epitaxial growth. Mg and Si doped GaN resulted in both p- and n-type materials.
Review
Materials Science, Multidisciplinary
Valentin Jmerik, Alexey Toropov, Valery Davydov, Sergey Ivanov
Summary: This review focuses on the recent progress in the development of monolayer-thick GaN/AlN multilayer heterostructures for deep-ultraviolet optoelectronics. The advantages of different epitaxial methods and characterization techniques are compared, while the optical properties of ML-thick GaN/AlN quantum wells and their potential in UVC emitter applications are investigated.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2021)
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
Materials Science, Coatings & Films
Iwan Susanto, Chi-Yu Tsai, Yen-Teng Ho, Ping-Yu Tsai, Ing-Song Yu
Summary: This study investigates the growth of GaN films on layered 2D-MoS2/c-sapphire substrate using a plasma-assisted molecular beam epitaxy system. The pre-nitridation process and growth duration are found to enhance the optical properties and crystal quality of the GaN films. The study also demonstrates a potential solution for the future applications of GaN-based devices.
SURFACE & COATINGS TECHNOLOGY
(2022)
Article
Chemistry, Multidisciplinary
Valentin Jmerik, Dmitrii Nechaev, Alexey Semenov, Eugenii Evropeitsev, Tatiana Shubina, Alexey Toropov, Maria Yagovkina, Prokhor Alekseev, Bogdan Borodin, Kseniya Orekhova, Vladimir Kozlovsky, Mikhail Zverev, Nikita Gamov, Tao Wang, Xinqiang Wang, Markus Pristovsek, Hiroshi Amano, Sergey Ivanov
Summary: This article discusses the use of GaN/AlN heterostructures for ultraviolet-C (UVC) emitters, employing multiple two-dimensional (2D) quantum disk/quantum well structures with varying GaN nominal thicknesses and AlN barrier layers. The growth process involved plasma-assisted molecular-beam epitaxy on c-sapphire substrates with a wide range of gallium and activated nitrogen flux ratios. By adjusting the Ga/N-2* ratio, the 2D-topography of the structures could be modified, leading to a variation in emission energy (wavelength). Electron-beam pumping was used to achieve high output optical power for different wavelength structures.
Article
Chemistry, Multidisciplinary
Valery Davydov, Evgenii M. Roginskii, Yuri Kitaev, Alexander Smirnov, Ilya Eliseyev, Eugene Zavarin, Wsevolod Lundin, Dmitrii Nechaev, Valentin Jmerik, Mikhail Smirnov, Markus Pristovsek, Tatiana Shubina
Summary: This study reveals that interface interdiffusion between GaN and AlN layers in short-period GaN/AlN superlattices has an effect on the Raman spectrum, with bands related to A(1)(LO) confined phonons being particularly sensitive. The correlation between Raman spectra and interface quality offers new possibilities for analyzing the structural characteristics of these superlattices.
Article
Chemistry, Multidisciplinary
Valery Davydov, Evgenii Roginskii, Yuri Kitaev, Alexander Smirnov, Ilya Eliseyev, Dmitrii Nechaev, Valentin Jmerik, Mikhail Smirnov
Summary: Experimental and theoretical studies were conducted on phonon modes in GaN/AlN superlattices, with results showing good agreement between calculations and experimental data, opening up new possibilities for analyzing structural characteristics using Raman spectroscopy and optimizing growth technologies.
Article
Physics, Applied
Reda Elwaradi, Jash Mehta, Thi Huong Ngo, Maud Nemoz, Catherine Bougerol, Farid Medjdoub, Yvon Cordier
Summary: In this study, two series of AlGaN/GaN/AlN high electron mobility transistor (HEMT) heterostructures were grown using molecular beam epitaxy. The effects of reducing the GaN channel thickness and varying the AlGaN barrier thickness and composition on the structural and electrical properties of the heterostructures were investigated. Material analysis techniques such as high-resolution x-ray diffraction, atomic force microscopy, and cross-sectional transmission electron microscopy were employed. The results showed that reducing the GaN channel thickness led to a decrease in GaN strain relaxation rate, but also caused degradation in crystal quality and electron mobility, along with an increase in sheet resistance. However, a trade-off was observed for a specific HEMT structure with a 50 nm width GaN channel, which exhibited a moderate sheet resistance and a high three-terminal breakdown voltage.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Engineering, Electrical & Electronic
Hao Yu, Alireza Alian, Uthayasankaran Peralagu, Ming Zhao, Niamh Waldron, Bertrand Parvais, Nadine Collaert
Summary: The density of AlGaN surface states was extracted and analyzed, showing the influence of AlN thickness on 2DEG density and AlGaN surface potential. The accuracy and factors affecting the DSS extraction method were demonstrated.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2021)
Article
Materials Science, Multidisciplinary
Reet Chaudhuri, Austin Hickman, Jashan Singhal, Joseph Casamento, Huili Grace Xing, Debdeep Jena
Summary: The study demonstrates that using a novel in situ crystalline AlN passivation layer can reduce surface state dispersion in AlN/GaN/AlN HEMTs, achieving higher output power. It is crucial to have thin GaN channel layers for growing thick AlN barrier layers without cracking. HEMTs fabricated on optimized heterostructures show lower dispersion compared to current state-of-art SiN-passivated HEMTs.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2022)
Article
Physics, Applied
Xiaopeng Wang, Gianluca Fabi, Reet Chaudhuri, Austin Hickman, Mohammad Javad Asadi, Kazuki Nomoto, Huili Grace Xing, Debdeep Jena, Marco Farina, James C. M. Hwang
Summary: Using a scanning microwave microscope (SMM), researchers have found that it is possible to characterize subsurface electromagnetic properties of nanoelectronic structures nondestructively. By removing the topography information, the sheet resistance of 2D electron or hole gas buried at the interface of a heterostructure can be extracted from the SMM data. This study is important for improving SMM technology and monitoring local sheet resistance during device manufacturing.
APPLIED PHYSICS LETTERS
(2022)
Article
Nanoscience & Nanotechnology
John G. Wright, Celesta S. Chang, David A. Muller, Huili G. Xing, Debdeep Jena
Summary: We investigate the structural and electronic properties of NbN/GaN junctions grown by plasma-assisted molecular beam epitaxy. High-quality NbN films grown on GaN exhibit superconductivity with critical temperatures above 10 K, even at thicknesses as low as 3 nm. We find that the NbN lattice follows the stacking sequence of the underlying GaN, with domain boundaries occurring at the atomic steps on the GaN surface. Through Schottky barrier diode measurements, we determine the barrier height of the NbN/GaN junction to be 1.3 eV.
Article
Physics, Applied
Wenwen Zhao, Mohammad Javad Asadi, Lei Li, Reet Chaudhuri, Kazuki Nomoto, Huili Grace Xing, James C. M. Hwang, Debdeep Jena
Summary: This study demonstrates the suspended AlN thin-film bulk acoustic resonators (FBARs) at 9.2 GHz in the X-band, showing promising performance and potential for integration with other devices for RF front end and microwave filter applications in quantum computing.
JOURNAL OF APPLIED PHYSICS
(2022)
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
Nanoscience & Nanotechnology
Jashan Singhal, Jimy Encomendero, Yongjin Cho, Len van Deurzen, Zexuan Zhang, Kazuki Nomoto, Masato Toita, Huili Grace Xing, Debdeep Jena
Summary: In this study, N-polar AlN epilayers were successfully grown on the N-face of AlN substrates using plasma-assisted molecular beam epitaxy. In situ thermal deoxidation and Al-assisted thermal desorption were used to remove native surface oxides and impurities, resulting in successful homoepitaxy. The grown AlN layer exhibited smooth surface morphologies and low structural defect densities, with the presence of interesting inversion domains.
Article
Multidisciplinary Sciences
Zexuan Zhang, Yusuke Hayashi, Tetsuya Tohei, Akira Sakai, Vladimir Protasenko, Jashan Singhal, Hideto Miyake, Huili Grace Xing, Debdeep Jena, YongJin Cho
Summary: Successful homoepitaxial growth of N-polar AlN has been achieved on large-area N-polar AlN templates using MBE. Al-assisted cleaning enables the epitaxial film to maintain N-polarity, resulting in a smooth, defect-free surface and suppression of nonradiative recombination centers.
Article
Physics, Applied
Shubham Jadhav, Ved Gund, Benyamin Davaji, Debdeep Jena, Huili (Grace) Xing, Amit Lal
Summary: This paper demonstrates a HZO-based ferroelectric NEMS unimorph as a fundamental building block for low-energy capacitive readout in-memory computing. The reported device achieves analog programmable control of the piezoelectric coefficient, demonstrating linear behavior and high computational throughput.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Joseph Casamento, Thai-Son Nguyen, Yongjin Cho, Chandrashekhar Savant, Timothy Vasen, Shamima Afroz, Daniel Hannan, Huili (Grace) Xing, Debdeep Jena
Summary: AlScN is an ideal choice as a lattice-matched epitaxial barrier layer for GaN high electron mobility transistors due to its large dielectric constant and polarization. The transport properties of the polarization-induced two-dimensional electron gas formed at the AlScN/GaN interface are studied, and it is found that the insertion of a nm AlN inter-layer can significantly enhance the mobility.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Micah S. S. Haseman, Daram N. N. Ramdin, Wenshen Li, Kazuki Nomoto, Debdeep Jena, Huili Grace Xing, Leonard J. J. Brillson
Summary: This study investigates the movement of electrically charged defects in Ga2O3 vertical trench power diodes using cathodoluminescence point spectra and hyperspectral imaging. The researchers observed the spatial rearrangement of optically active defects under strong reverse bias. These findings demonstrate the potential impact of extreme electric fields on atomic rearrangement and local doping changes in beta-Ga2O3, highlighting the importance of nanoscale device geometry in other high-power semiconductor devices.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Nanoscience & Nanotechnology
Jashan Singhal, Reet Chaudhuri, Austin Hickman, Vladimir Protasenko, Huili Grace Xing, Debdeep Jena
Summary: Due to its high breakdown electric field, the ultra-wide bandgap semiconductor AlGaN has gained attention as a potential channel material for next-generation high electron mobility transistors (HEMTs). However, there is a lack of comprehensive experimental study on the effects of Al composition on the transport and structural properties. In this study, we systematically varied the Al content in strained AlGaN quantum well channels to investigate the charge control and transport properties of polarization-induced 2D electron gases (2DEGs). The results showed that the 2DEG density can be tuned by adjusting the Al content.
Article
Physics, Applied
Zexuan Zhang, Jashan Singhal, Shivali Agrawal, Eungkyun Kim, Vladimir Protasenko, Masato Toita, Huili Grace Xing, Debdeep Jena
Summary: Polarization-induced carriers are important for achieving high electrical conductivity in ultrawide bandgap semiconductor AlGaN. However, studies on these carriers in N-polar AlGaN are rare. This study observes and characterizes polarization-induced two-dimensional electron gases (2DEGs) in N-polar AlGaN/AlN heterostructures with varying Al content. The results provide valuable insights for designing high electron mobility transistors and UV photonic devices.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Jashan Singhal, Eungkyun Kim, Austin Hickman, Reet Chaudhuri, Yongjin Cho, Huili Grace Xing, Debdeep Jena
Summary: We conducted a study on the compositional dependence of electrical characteristics in AlxGa1-xN quantum well channel-based AlN/AlGaN/AlN high electron mobility transistors (HEMTs), with x values of 0.25, 0.44, and 0.58. The use of selectively regrown n-type GaN Ohmic contacts resulted in increased contact resistance with higher Al content in the channel. The DC HEMT device characteristics showed a progressive reduction in maximum drain current densities and a simultaneous decrease in threshold voltage with increasing x values.
APPLIED PHYSICS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Wenwen Zhao, Mohammad Javad Asadi, Lei Li, Reet Chaudhuri, Kazuki Nomoto, Huili Grace Xing, James C. M. Hwang, Debdeep Jena
Summary: This study demonstrates epitaxial AlN thin-film bulk acoustic resonators (FBARs) on SiC substrates with first-order thickness extensional modes of 15-17 GHz. The achieved quality factor Q(max) of approximately 443, electromechanical coupling coefficient k(eff)(2) of approximately 2.3%, and f center dot Q of approximately 6.65 THz figure of merit are among the highest in the Ku-band (12-18 GHz). The clean primary mode with a high quality factor allows these epitaxial AlN FBARs to be used in Ku-band acoustic filters with clean bands and steep rejection. Additionally, their compatibility with AlN/GaN/AlN quantum well high-electron-mobility transistors (QW HEMTs) allows for monolithic integration with HEMT low noise amplifiers (LNAs) and power amplifiers (PAs).
IEEE ELECTRON DEVICE LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Gustavo A. Alvarez, Joseph Casamento, Len van Deurzen, Md Irfan Khan, Kamruzzaman Khan, Eugene Jeong, Elaheh Ahmadi, Huili Grace Xing, Debdeep Jena, Zhiting Tian
Summary: Aluminum scandium nitride (AlScN) is gaining attention for its larger piezoelectric response compared to AlN, but alloying Sc with AlN reduces thermal conductivity. Self-heating limits power handling in AlScN devices, and we compared thermal conductivity of AlScN grown on different substrates.
MATERIALS RESEARCH LETTERS
(2023)
