Article
Quantum Science & Technology
Zachariah O. Martin, Alexander Senichev, Samuel Peana, Benjamin J. Lawrie, Alexei S. Lagutchev, Alexandra Boltasseva, Vladimir M. Shalaev
Summary: A robust process for fabricating intrinsic single-photon emitters in silicon nitride has been established, showing promise for quantum applications. The photophysical properties of these emitters are probed through measurements of optical transition wavelengths, linewidths, and photon antibunching as a function of temperature. Insight into the potential for lifetime-limited linewidths is provided through measurements of inhomogeneous and temperature-dependent broadening of the zero-phonon lines.
ADVANCED QUANTUM TECHNOLOGIES
(2023)
Review
Chemistry, Multidisciplinary
Deshabrato Mukherjee, Peter Petrik
Summary: Ellipsometry stands out among real-time characterization methods for its high sensitivity and speed, as well as nondestructive, spectroscopic, and complex modeling capabilities. It can determine the thicknesses and complex dielectric function of thin films with precisions down to sub-nanometer and 10-4, respectively. Since the late 1960s, ellipsometry has been widely used in monitoring layer growth and determining optical properties of metals, semiconductors, and superconductors. It serves as a steady alternative to nonpolarimetric spectroscopies for obtaining quantitative information in complex layered structures.
Article
Materials Science, Multidisciplinary
Ramasis Goswami, Syed Qadri, Neeraj Nepal, Charles Eddy
Summary: In this study, ultra-thin AlN films were grown on different substrates using atomic layer epitaxy, showing that the substrate, particularly the strain, plays a crucial role in determining the crystal structure of AlN films. The strain level varied significantly depending on the substrate, impacting the orientation relation and crystal quality of AlN films.
Article
Materials Science, Multidisciplinary
Jae Chan Park, Dae Hyun Kim, Tae Jun Seok, Dae Woong Kim, Ji-Hoon Ahn, Woo-Hee Kim, Tae Joo Park
Summary: We have successfully fabricated high-quality atomic-layer-deposited SiNx thin films at a low temperature of 300℃ using a novel remote plasma source called hollow cathode plasma (HCP). Compared to SiNx films deposited using the conventional remote plasma source, inductively-coupled plasma (ICP), the SiNx films grown using the HCP source exhibit superior properties. They have a higher N/Si ratio, lower oxygen impurity concentration, and exceptional oxidation resistance. Additionally, the HCP SiNx films show improved wet etch rate and excellent electrical properties, such as dielectric constant, gate leakage current, and dielectric breakdown field.
JOURNAL OF MATERIALS CHEMISTRY C
(2023)
Article
Chemistry, Multidisciplinary
Dawson B. Bonneville, Jeremy W. Miller, Caitlin Smyth, Peter Mascher, Jonathan D. B. Bradley
Summary: The study reports on the deposition of high-optical quality silicon nitride thin films under low-temperature and low-pressure conditions using ECR-PECVD technology. The as-deposited films exhibit variable compositions with significant oxygen content and hydrogen incorporation.
APPLIED SCIENCES-BASEL
(2021)
Article
Materials Science, Ceramics
Zilong Lu, Zhe Qi, Jinhua Yang, Hu Liu, Jian Jiao
Summary: Boron nitride (BN) coatings with a thickness of 20-40 μm were prepared on graphite substrates by chemical vapor deposition. The wettability of the BN coatings with deionized water was influenced by the deposition temperature, with a rapid increase in wetting angle at 1100-1250°C and a wetting-to-nonwetting transition. The contact angle or nonwettability increased with higher crystallinity and lower surface roughness, which were controlled by the deposition temperature. The wetting angle increased (650-950°C), then decreased (950-1100°C), and again increased rapidly (1100-1250°C), leading to the wetting-to-nonwetting transition (1100-1250°C).
INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY
(2023)
Article
Chemistry, Multidisciplinary
Maximilian Prechtl, Shayan Parhizkar, Oliver Hartwig, Kangho Lee, Josef Biba, Tanja Stimpel-Lindner, Farzan Gity, Andreas Schels, Jens Bolten, Stephan Suckow, Anna Lena Giesecke, Max C. Lemme, Georg S. Duesberg
Summary: This paper introduces a low-temperature growth method for layered platinum diselenide and discusses its application in the integration of silicon photonics devices. The new growth method provides a new design route for synthesizing 2D materials with more complex structures.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Christopher Perez, Aaron J. Mcleod, Michelle E. Chen, Su-In Yi, Sam Vaziri, Ryan Hood, Scott T. Ueda, Xinyu Bao, Mehdi Asheghi, Woosung Park, A. Alec Talin, Suhas Kumar, Eric Pop, Andrew C. Kummel, Kenneth E. Goodson
Summary: Aluminum nitride (AlN) is an electrically insulating material with excellent thermal conductivity. This study demonstrates the deposition of AlN films at low temperatures using sputtering, and analyzes their thermal properties based on grain size and interfacial quality. The results show that varying the partial pressure of reactive N2 can significantly alter the thermal conductivity of the films, and the defect densities can be estimated from the measurements, providing insights for optimizing the thermal engineering of AlN.
Article
Materials Science, Ceramics
Chunxi Luo, Yaxiang Zhang, Tengfei Deng
Summary: The addition of MgO-LiF in Si3N4 ceramics enhances their mechanical and thermal properties, resulting in higher relative density at specific content levels.
CERAMICS INTERNATIONAL
(2021)
Article
Materials Science, Ceramics
Rong Tu, Zhen Liu, Qingfang Xu, Song Zhang, Qizhong Li, Xian Zhang, Marina L. Kosinova, Takashi Goto
Summary: Silicon nitride films were fabricated using halide laser chemical vapor deposition (LCVD) for surface protection of electronic devices. The study investigated the effects of deposition parameters on the crystallinity, microstructure, deposition rate, Vickers microhardness, nano-hardness, and electrical resistivity. The highest deposition rate was achieved at a temperature of 1573 K and pressure of 10 kPa. The hardness of the films increased with temperature and the electrical resistivity decreased.
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
(2023)
Article
Materials Science, Ceramics
Yang Liu, Wei-Ming Guo, Kun-Heng Huang, Hua-Tay Lin
Summary: This study investigates the toughening effects of SiC nanowires and SiC whiskers on high-entropy carbide based composites at different temperatures. The results show that SiC nanowires and SiC whiskers have good toughening effects at low temperature, but their mechanical properties are significantly reduced at high temperature.
INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY
(2023)
Article
Physics, Applied
K. Nozawa, T. Ishiyama, T. Nishida, N. Saitoh, N. Yoshizawa, T. Suemasu, K. Toko
Summary: Using our solid-phase crystallization technology, we successfully synthesized n-type polycrystalline Ge thin films with the highest recorded electron mobility (450 cm(2) V-1 s(-1)) on insulating substrates. The density and barrier height of grain boundaries in the P-doped polycrystalline Ge layers were controlled by the underlayer type and a small amount of Sn addition. By growing at a low temperature (<400°C), we developed a GeSn layer on a heat-resistant polyimide film with the highest electron mobility (200 cm(2) V-1 s(-1)), directly on a flexible substrate. These achievements pave the way for high-performance polycrystalline Ge-based devices on inexpensive glass and flexible plastic substrates.
APPLIED PHYSICS LETTERS
(2023)
Article
Optics
The Anh Nguyen, Ming-Chang M. Lee
Summary: An ultra-thin Si-padded Si3N4 waveguide was proposed, with a very thin Si slab and a Si3N4 strip separated by a SiO2 layer. The measured waveguide propagation loss is low at 0.055 dB/cm, and the bending loss is within an acceptable range. Part of the waveguide mode is distributed in the Si slab, showing potential for low-loss and high-speed photonic integrated circuits.
Article
Astronomy & Astrophysics
Joerg Jaeckel, Wen Yin
Summary: We discuss baryogenesis in scenarios where the Universe is reheated to low temperatures by the decay of long-lived massive particles into energetic SM particles. Optimistic estimates suggest that successful baryogenesis is possible even for low reheating temperatures. The enhancement of the W-boson coupling in an extended SM model can achieve sufficient baryon production.
Article
Crystallography
Johannes Steiner, Jana Schultheiss, Shouzhong Wang, Peter J. Wellmann
Summary: SiC-on-insulator (SiCOI) substrates offer new device designs for electronic switches and photonic applications. In this study, a deposition temperature below 1200 degrees C and a non-water-cooled system were used to successfully deposit 3C-SiC epitaxial layer substrates on SOI, without delamination.
Article
Chemistry, Physical
Tarni Aggarwal, Swaroop Ganguly, Dipankar Saha
Summary: This study explores the use of GaN-based quantum-confined structures with optical cavities for solid-state light sources. It reveals that variations in stoichiometry and the presence of recombination centers do not necessarily lead to sub-bandgap transitions, as trapped electrons can be recovered through Coulombic interaction. The presence of carrier reservoirs in the form of inhomogeneities can significantly reduce the efficacy of sub-bandgap transitions, as evidenced by time-resolved measurements.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Article
Engineering, Electrical & Electronic
Bazila Parvez, Jaya Jha, Pankaj Upadhyay, Navneet Bhardwaj, Yogendra Yadav, Bhanu Upadhyay, Swaroop Ganguly, Dipankar Saha
Summary: Thinning of the SiC substrate has positive effects on the performance of AlGaN/GaN HEMTs, including reducing contact resistance, increasing mobility and saturation velocity, and decreasing 2DEG density. Overall, these effects collectively contribute to the performance improvement of the devices.
IEEE ELECTRON DEVICE LETTERS
(2021)
Article
Chemistry, Physical
Navneet Bhardwaj, Bhanu B. Upadhyay, Yogendra K. Yadav, Sreenadh Surapaneni, Swaroop Ganguly, Dipankar Saha
Summary: In this study, 10 nm of amorphous Nb2O5 was successfully grown on an AlGaN/GaN heterostructure, with ideal stoichiometry and a band gap of 4.15 eV determined by XPS analysis. Additionally, TEM confirmed the thickness and crystallinity of the oxide, while AFM measured a RMS roughness of 1.32 nm. The capacitive behavior of Nb2O5 and its interface characteristics with AlGaN were estimated by CV characteristics.
APPLIED SURFACE SCIENCE
(2022)
Article
Engineering, Electrical & Electronic
Vikas Pendem, Swaroop Ganguly, Dipankar Saha
Summary: In this study, we have investigated the fractional dimensional nature of experimental semiconductor quantum mechanical systems and its effect on the accurate prediction of electronic and optoelectronic properties. We have proposed a formalism to estimate the actual dimensionality of the system, which addresses the anomaly of using the conventional integer density of states (DOS). We have experimentally verified the formalism in AlGaN/GaN high electron mobility transistors (HEMTs) and observed a significant variation in dimensionality as the gate bias sweeps the channel from depletion to strong inversion. Furthermore, we have observed the manifestation of fractional dimension in AlGaN/GaN nanofins, which is verified experimentally through a shift in threshold voltage and the rate of conduction-band state filling. Thus, this efficient and accurate formalism enhances the accuracy of models by estimating the dimension of any quantum mechanical system.
IEEE TRANSACTIONS ON NANOTECHNOLOGY
(2022)
Article
Nanoscience & Nanotechnology
Tarni Aggarwal, Ankit Udai, Pratim K. Saha, Swaroop Ganguly, Pallab Bhattacharya, Dipankar Saha
Summary: Efficiency droop at high carrier-injection regimes is a concern in InGaN/GaN quantum-confined hetero-structure-based light-emitting diodes (LEDs). This study demonstrates a potential solution through the positive effects from an optical cavity in suppressing the Auger recombination rate and highlights its technological importance.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Materials Science, Multidisciplinary
Bhanu B. Upadhyay, Sreenadh Surapaneni, Yogendra K. Yadav, Navneet Bhardwaj, Netaji Suvachintak, Swaroop Ganguly, Dipankar Saha
Summary: Utilizing Ta2O5 high-k gate dielectric-based GaN high electron-mobility transistors can achieve high I(ON)/I(OFF) ratio and low gate leakage current without significant deterioration of other performance parameters.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2022)
Article
Materials Science, Multidisciplinary
Akhil S. Kumar, Swaroop Ganguly, Dipankar Saha
Summary: Through partial overlapping gate transistors, a trade-off can be found between gate leakage current, I-OFF, and I-ON/I-OFF.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2022)
Article
Engineering, Electrical & Electronic
M. Meer, P. Pohekar, B. Parvez, S. Ganguly, D. Saha
Summary: In this study, the thermal oxidation of nickel as gate dielectrics is used to improve the characteristics of GaN-based metal oxide semiconductor high electron mobility transistors (HEMTs). The use of NiO as the gate dielectric leads to significant improvements in drive current, transconductance, subthreshold swing, unity current gain frequency, and gate current leakage. Additionally, a positive shift in threshold voltage is observed for the NiO-based gate dielectric devices compared to the Schottky barrier HEMTs.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2022)
Article
Nanoscience & Nanotechnology
Ankit Udai, Swaroop Ganguly, Pallab Bhattacharya, Dipankar Saha
Summary: This study investigates the ultrafast carrier dynamics of bound states in In0.14Ga0.86N/GaN quantum wells using femtosecond transient absorption spectroscopy. It reveals that both the ground and excited states contribute to the overall dynamics, which can be decoupled in the absorption spectra and time-resolved dynamics.
Article
Materials Science, Multidisciplinary
Vivek Kumar Surana, Swaroop Ganguly, Dipankar Saha
Summary: This work demonstrates the performance improvements in AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) achieved by using low-temperature inductively coupled plasma chemical vapor deposited (ICP-CVD) silicon nitride (SiNx). The SiNx layer effectively increases the in-plane tensile strain in the AlGaN barrier layer, leading to enhanced conductivity and piezoelectric properties of the transistor.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2022)
Article
Engineering, Electrical & Electronic
Binit Mallick, Dipankar Saha, Anindya Datta, Swaroop Ganguly
Summary: In this study, a physics-based numerical modeling approach is proposed to analyze experimental time-dependent optical second harmonic generation data from an oxide/semiconductor (SiO2/Si) interface. The comprehensive numerical solution to the Poisson-Boltzmann equation is developed using the Newton-Raphson method at different time instances. It incorporates the trapping behavior of photo-excited charge carriers at the SiO2/Si interface, within the SiO2, and at the SiO2 surface, in order to model the second harmonic photon count data obtained from experiments. This method enables quantitative analysis of the interface, oxide, and surface charge densities, providing a contact-less and non-invasive optical technique for oxide/semiconductor interface characterization.
SOLID-STATE ELECTRONICS
(2023)
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, Multidisciplinary
Navneet Bhardwaj, Bhanu B. Upadhyay, Bazila Parvez, Prachi Pohekar, Yogendra Yadav, Arpit Sahu, Mahalaxmi Patil, Subhajit Basak, Jyoti Sahu, Farheen Shamim Ahmed Sabiha, Swaroop Ganguly, Dipankar Saha
Summary: This study demonstrates the improvement in DC and RF characteristics and a reduction in gate leakage current with thermally grown Nb2O5 in AlGaN/GaN MOS-HEMTs. The amorphous Nb2O5 gate dielectric reduces gate leakage current and enhances the device performance.
Article
Nanoscience & Nanotechnology
Binit Mallick, Dipankar Saha, Anindya Datta, Swaroop Ganguly
Summary: This article presents a non-destructive and contactless characterization method for semiconductor/dielectric interfaces based on optical second-harmonic generation (SHG) technique. It can measure the conduction band offset and quantitatively evaluate the charge densities at the interface. The method extracts the type of interface-trapped charge and qualitatively analyzes the variation in interface states and oxide surface state density. A developed optical setup is used to monitor the time-dependent SHG from the semiconductor/oxide interface, and a numerical solver is employed to model the experimental data and extract the electronic properties at the interface.
ACS APPLIED MATERIALS & INTERFACES
(2023)