Article
Optics
Katarzyna Pieniak, Witold Trzeciakowski, Grzegorz Muziol, Anna Kafar, Marcin Siekacz, Czeslaw Skierbiszewski, Tadeusz Suski
Summary: The study examined electroluminescence from In0.17Ga0.83N/GaN quantum wells of LEDs and LDs, finding a transition from ground-states recombination to excited states recombination with increasing QW width. The effect is accompanied by partial or complete screening of the built-in electric field with increasing driving current, which was studied using a high pressure method. Investigations were supported by simulations of the variation with driving current of electron and hole wavefunctions overlap affecting the recombination channel and built-in electric field.
Article
Physics, Applied
Shixiong Zhang, Ning Tang, Zhenhao Sun, Guoping Li, Teng Fan, Lei Fu, Yunfan Zhang, Jiayang Jiang, Peng Jin, Weikun Ge, Bo Shen
Summary: The correlation between spin-polarized carrier transfer and spin relaxation processes of a 2DEG in an InGaN/GaN quantum well is investigated. It is found that by tailoring the spin-orbit couplings, the spin relaxation time can be enhanced, which is significant for the development of GaN-based spintronic devices.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Liwen Cheng, Zhenwei Li, Jiayi Zhang, Xingyu Lin, Da Yang, Haitao Chen, Shudong Wu, Shun Yao
Summary: An InGaN laser diode with InGaN-GaN-InGaN delta barriers demonstrates lower turn-on current, higher laser power, and higher slope efficiency compared to those with InGaN or conventional GaN barriers. These improvements are attributed to modified energy bands that enhance carrier injection within the active region.
Article
Physics, Applied
K. H. Li, Y. F. Cheung, W. Y. Fu, H. W. Choi
Summary: The combination of high-quality factors and small mode volumes in whispering-gallery-mode (WGM) resonators promotes significantly enhanced light-matter interactions, making them excellent cavities for achieving compact semiconductor lasers with low threshold and narrow linewidth. The researchers report on WGM emission from vertical-injection blue-light emitting InGaN/GaN thin-film microdisks achieved by wafer bonding and laser liftoff removal of the sapphire substrate, showing high Q-factors. This work presents a viable approach toward the practical implementation of compact InGaN/GaN microdisk lasers through a simple and scalable process.
APPLIED PHYSICS LETTERS
(2021)
Article
Optics
A. Bercha, W. Trzeciakowski, G. Muziol, J. W. Tomm, T. Suski
Summary: Wide InGaN/GaN quantum wells in LED structures with a size of 15-25 nm were compared with narrow wells with a size of 2.6 nm using time-resolved photoluminescence spectroscopy. The study observed that wide wells exhibited slow increase and fast decay of photoluminescence pulses under low-intensity excitation, and the shape of the pulses changed with varying separation. These effects were not observed in samples with narrow wells. The unusual properties of wide wells were attributed to the presence of dark charge, which effectively screened the built-in field in the well, leading to the appearance of excited states and photoluminescence.
Article
Nanoscience & Nanotechnology
K. Khan, S. Diez, Kai Sun, C. Wurm, U. K. Mishra, E. Ahmadi
Summary: This study reports the observation of self-assembled InGaN/(In)GaN superlattice structure in InGaN film grown on N-polar GaN substrate, with varying In content in each layer depending on growth temperature. By increasing the substrate temperature, a periodic structure was achieved, offering a new pathway for designing and fabricating electronic and optoelectronic devices with enhanced performance.
Article
Physics, Applied
Sangeeta Singh, Pallavi Kumari
Summary: This study reports a novel n-type GaN/InGaN/GaN heterostructure vertical double-gate tunnel field-effect transistor (VTFET) using thorough calibrated simulation. By introducing a polarization layer near the source-channel junction, the drain current is increased due to the increase in charge concentration near the interface. The optimized structure with HfO2 as the dielectric material achieves excellent performance in terms of dc and analog/RF properties, making it a promising alternative for high-power steep switching analog and RF applications.
INTERNATIONAL JOURNAL OF MODERN PHYSICS B
(2023)
Article
Physics, Applied
Dan-Na Liu, Sha-Sha Ke, Rui-Yang Yuan, Yong Guo
Summary: Two types of WS2/MoX2/WS2 (X = S, Se) planar heterostructures driven by bias are proposed and studied, showing pronounced negative differential resistance (NDR) effect. The study demonstrates that the maximum peak-to-valley ratio (mPVR) and current peak strongly depend on temperature, and enhanced mPVR can be achieved by tuning the device length. Type B (X = Se) exhibits a more remarkable NDR effect compared to Type A (X = S). This work provides promising possibilities for designing and manufacturing future low-power electronic devices based on monolayer transition metal dichalcogenide planar heterostructures under low bias regime.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Physical
Li Liu, Qingqing Feng, Yu Zhang, Xiaolu Zhu, Lanli Chen, Zhihua Xiong
Summary: Improving the luminescence efficiency of long wavelength InGaN-based LEDs is a challenging task, and strain-induced piezoelectric effect has been shown to be an effective measure. Reduction of valence band offset at InGaN/GaN heterointerfaces significantly improves hole injection. Tensile strain in the GaN film on a silicon substrate increases the overlap of electron and hole wave functions, leading to enhanced efficiency. Control of the strain-induced piezoelectric polarisation of the InGaN quantum well layer further improves the internal quantum efficiency.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Bumsu Park, Ja Kyung Lee, Christoph T. Koch, Martin Woelz, Lutz Geelhaar, Sang Ho Oh
Summary: Growing an InxGa1-xN/GaN multi-quantum well heterostructure in nanowire form can overcome limitations in conventional planar heterostructure LEDs by relaxing the strain induced in the heterostructure through the sidewalls of the nanowire. This study demonstrates techniques for mapping the complex strain distribution within an In0.3Ga0.7N/GaN MQW heterostructure embedded in a GaN nanowire and provides insights into the strain-induced piezoelectric fields in nanowire LEDs.
Article
Engineering, Electrical & Electronic
Shumeng Yan, Yu Zhou, Jianxun Liu, Yaozong Zhong, Xiujian Sun, Xin Chen, Xiaolu Guo, Qian Li, Qian Sun, Hui Yang
Summary: The influence of energy band structure on the electrical characteristics of GaN-based DHBTs was studied through simulation and fabrication. A novel DHBT structure with a composition graded base was grown and fabricated, achieving a long minority carrier lifetime of 4.08 ns. The elimination of the energy barrier at the conventional GaN/InGaN/GaN B-C junction interface was proposed by combining indium composition grading of the p-InGaN base layer and Si doping profile tuning for the collector layer. The as-fabricated DHBT presented a high intercept voltage of 225 V and a high current gain of 49.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Optics
Pradip Dalapati, Kosuke Yamamoto, Takashi Egawa, Makoto Miyoshi
Summary: The degradation characteristics of InGaN/GaN multiple quantum well (MQW) photodetectors (PDs) under 100 and 200 mA current stress for 480 hours were investigated. The results showed that the luminescence intensity, short circuit current density, and open circuit voltage decrease significantly, while the leakage current increases intensely under constant current stress. Additionally, the photocurrent spectroscopy results revealed changes in the peak value of relative external quantum efficiency (EQE) under different stress currents.
Article
Physics, Applied
Pratim K. Saha, Kanchan Singh Rana, Navneet Thakur, Bazila Parvez, Shazan Ahmad Bhat, Swaroop Ganguly, Dipankar Saha
Summary: In this study, room-temperature single-photon emission from an InGaN QD embedded in a GaN nanoneedle is demonstrated. Reproducible and uniform-sized QDs are formed in the needle structures through a series of nanofabrication process steps. The results show higher spectral purity and smaller values of the second-order correlation, indicating the usefulness of the methodology for quantum technologies.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Abu Bashar Mohammad Hamidul Islam, Tae Kyoung Kim, Dong-Soo Shin, Jong-In Shim, Joon Seop Kwak
Summary: This study investigates the effect of current stress on InGaN/GaN multiple-quantum-well flip-chip blue micro light-emitting diodes (mu-LEDs) and reveals the mechanisms of defect aggregation and generation that cause changes in the optoelectronic performance of the devices. The aging test shows that the improvement in crystal quality due to defect aggregation initially enhances the light output power and external quantum efficiency (EQE), but the generation of sidewall point defects eventually leads to performance degradation. The findings highlight the importance of both defect aggregation and generation in understanding the degradation mechanisms of mu-LEDs.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Physical
Do-Yeong Shin, Taehwan Kim, Ozgun Akyuz, Hilmi Volkan Demir, In-Hwan Lee
Summary: This study presents an improved efficiency design for white LEDs by integrating blue nanorod LEDs with green and red-emitting perovskite nanocrystal films. The design utilizes the localized surface plasmon effect of Ag@SiO2 nanoparticles to enhance the photoluminescence intensity of blue LEDs, while the high-power blue LED backlight improves the perovskite photoluminescence intensity. The resulting white LED with Ag@SiO2 nanoparticle-embedded nanorods demonstrates a 62% increase in photoluminescence intensity compared to planar white LEDs.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
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)
Review
Chemistry, Multidisciplinary
Xiaodong Yan, Justin H. Qian, Vinod K. Sangwan, Mark C. Hersam
Summary: The increasing importance of artificial intelligence has led to the development of neuromorphic circuits that aim to replicate the energy-efficient information processing of the brain. This review provides a conceptual overview of memtransistors in the context of neuromorphic circuits and surveys recent progress in this field. The different materials systems and device architectures are classified based on their control and tunability of synaptic behavior, with a focus on nanomaterials and their unique properties. Strategies for wafer-scale integration and materials challenges for practical neuromorphic circuits are also discussed.
ADVANCED MATERIALS
(2022)
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
Physics, Applied
John M. Cain, Xiaodong Yan, Stephanie E. Liu, Justin H. Qian, Thomas T. Zeng, Vinod K. Sangwan, Mark C. Hersam, Stanley S. Chou, Tzu-Ming Lu
Summary: Sulfur-deficient polycrystalline two-dimensional molybdenum disulfide memtransistors demonstrate gate-tunable memristive switching for new memory operations and neuromorphic computing paradigms. The influence of grain boundaries, sulfur vacancies, and surface interactions on defect-related kinetics that produces memristive switching is studied using current transient measurements. It is observed that adsorbed water molecules alter the resistive switching kinetics by suppressing the electronic trap-filling processes.
APPLIED PHYSICS LETTERS
(2023)
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
Engineering, Electrical & Electronic
Xiaodong Yan, Justin H. Qian, Jiahui Ma, Aoyang Zhang, Stephanie E. Liu, Matthew P. Bland, Kevin J. Liu, Xuechun Wang, Vinod K. Sangwan, Han Wang, Mark C. Hersam
Summary: This study presents a reconfigurable mixed-kernel transistor based on dual-gated van der Waals heterojunctions for low-power off-grid medical data classification and diagnosis applications. The experimental results show that this transistor can generate fully tunable Gaussian and sigmoid functions for arrhythmia detection from electrocardiogram signals with high classification accuracy. Additionally, the reconfigurable nature of this transistor allows for personalized detection. Compared to conventional complementary metal-oxide-semiconductor circuits, a single mixed-kernel heterojunction transistor provides a low-power approach for support vector machine classification applications.
NATURE ELECTRONICS
(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)
