Article
Nanoscience & Nanotechnology
Mohamadali Malakoutian, Daniel E. Field, Nicholas J. Hines, Shubhra Pasayat, Samuel Graham, Martin Kuball, Srabanti Chowdhury
Summary: The implementation of SG-and-beyond networks requires faster, high-performance, and power-efficient semiconductor devices, with gallium nitride (GaN) power amplifiers playing a crucial role in providing high frequency and power output. Cooling GaN devices with diamond has gained significant momentum in overcoming heat removal challenges, achieving record-low thermal boundary resistance at the diamond/GaN interface. Integration of diamond within close proximity to the GaN channel layer without degrading electrical behavior, along with the growth of isotropic polycrystalline diamond, has led to an efficient heat spread in both vertical and lateral directions. The impressive combination of thermal conductivity and low thermal boundary resistance marks a leading-edge achievement in this field.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Review
Engineering, Electrical & Electronic
Subhajit Mohanty, Kamruzzaman Khan, Elaheh Ahmadi
Summary: In recent years, GaN has become the material of choice for high power switching, high power RF and lighting applications. N-polar nitride heterostructures can provide benefits for these applications due to their intrinsic material properties. This article reviews the electronic and optical properties of N-polar (In, Ga, Al)N thin films and heterostructures, as well as the techniques used for their epitaxial growth. It also presents important process technologies developed for fabrication of N-polar GaN high electron mobility transistors.
PROGRESS IN QUANTUM ELECTRONICS
(2023)
Article
Chemistry, Multidisciplinary
Mohamadali Malakoutian, Chenhao Ren, Kelly Woo, Haoran Li, Srabanti Chowdhury
Summary: The integration of polycrystalline diamond on nitrogen-polar GaN was achieved using a two-stage-three-step growth recipe, which maintained device performance while significantly reducing channel temperature. This novel approach utilized a standard 5 nm Si3N4 layer as an interlayer for etching protection during growth, leading to improved thermal management of GaN-based devices for 5G networks.
CRYSTAL GROWTH & DESIGN
(2021)
Article
Chemistry, Physical
Jerome A. Cuenca, Matthew D. Smith, Daniel E. Field, Fabien C-P Massabuau, Soumen Mandal, James Pomeroy, David J. Wallis, Rachel A. Oliver, Iain Thayne, Martin Kuball, Oliver A. Williams
Summary: The study investigates the thermal stresses induced by diamond directly deposited onto III-nitride (III-N) heterostructure membranes, using analytical methods, numerical models, and experimental validation. It is found that the thermal stresses are mainly caused by the mismatch in coefficient of thermal expansion (CTE), and can be reduced by pre-stressing the membrane.
Article
Chemistry, Multidisciplinary
Jianbo Liang, Ayaka Kobayashi, Yasuo Shimizu, Yutaka Ohno, Seong-Woo Kim, Koji Koyama, Makoto Kasu, Yasuyoshi Nagai, Naoteru Shigekawa
Summary: The direct integration of GaN and diamond for high-power devices faces challenges due to mismatch in lattice and thermal-expansion coefficients. A successful fabrication of GaN/diamond heterointerface was achieved using a surface activated bonding method at room temperature. An intermediate layer composed of amorphous carbon and diamond is formed at the interface, with Ga and N atoms diffusing during the bonding process and transitioning to diamond after annealing.
ADVANCED MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Ryo Kagawa, Zhe Cheng, Keisuke Kawamura, Yutaka Ohno, Chiharu Moriyama, Yoshiki Sakaida, Sumito Ouchi, Hiroki Uratani, Koji Inoue, Yasuyoshi Nagai, Naoteru Shigekawa, Jianbo Liang
Summary: This study demonstrates the potential of fabricating GaN HEMTs on diamond substrates by successfully transferring AlGaN/GaN/3C-SiC layers to large diamond substrates and maintaining the integrity and high thermal conductivity of the substrate interface. It enables high-quality crystal growth and excellent heat dissipation performance.
Article
Chemistry, Physical
Fengwen Mu, Bin Xu, Xinhua Wang, Runhua Gao, Sen Huang, Ke Wei, Kai Takeuchi, Xiaojuan Chen, Haibo Yin, Dahai Wang, Jiahan Yu, Tadatomo Suga, Junichiro Shiomi, Xinyu Liu
Summary: Efficient heat dissipation is crucial for achieving high device performance and reliability in gallium nitride (GaN)-based high electron mobility transistors (HEMTs). This study explores the use of modified surface activated bonding (SAB) to prepare GaN-diamond bonded composites with silicon interlayers of different thicknesses. The thermal boundary conductance (TBC) and stress of the bonded interface are investigated before and after annealing, revealing the effects of interlayer thickness and annealing on TBC and thermal stability.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Engineering, Electrical & Electronic
Xinyu Zhou, Mohamadali Malakoutian, Rohith Soman, Zhengliang Bian, Rafael Perez Martinez, Srabanti Chowdhury
Summary: This article presents a modeling approach and implementation to study the impact of top-side diamond integration on the performance of a mm-wave GaN HEMT. The simulation results guide the optimization of RF performance and aid in the device design of diamond passivation.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Materials Science, Multidisciplinary
Wenqiang Xu, Shengrui Xu, Hongchang Tao, Yuan Gao, Xiaomeng Fan, Jinjuan Du, Lixia Ai, Liping Peng, Jinfeng Zhang, Jincheng Zhang, Yue Hao
Summary: By using an h-BN insertion layer, single crystal GaN film was successfully grown on a polycrystalline diamond substrate, addressing the challenge of combining GaN and diamond. Through process optimization, the full width at half maximum and surface roughness of GaN film were significantly reduced, while the yellow luminescence caused by carbon impurity was suppressed. This successful preparation offers a new solution to the heat dissipation issue that has hindered the development of GaN-based power devices.
Article
Materials Science, Ceramics
Yi Wang, Haining Ji, Yongxing Chen, Bin Liu, Jiamei Huang, Mingying Lu, Yangyong Ou, Yong Zhao, Jundong Tao, Yan Huang, Junlong Wang
Summary: Controlling the cooling effect in radiative cooling is a major challenge. This paper proposes a novel radiative cooling device that addresses this challenge by adjusting materials and stress to achieve different cooling modes. The device demonstrates excellent energy-saving capabilities in high-temperature environments and prevents excessive cooling in low-temperature environments.
CERAMICS INTERNATIONAL
(2023)
Article
Chemistry, Multidisciplinary
Joonghoon Choi, Junseok Jeong, Xiangyu Zhu, Junghwan Kim, Bong Kyun Kang, Qingxiao Wang, Bo-In Park, Seokje Lee, Jekyung Kim, Hyunseok Kim, Jinkyoung Yoo, Gyu-Chul Yi, Dong-Seon Lee, Jeehwan Kim, Suklyun Hong, Moon J. Kim, Young Joon Hong
Summary: This study investigates the thermochemical stability of graphene on GaN substrate and discovers the unexpected stability of graphene on N-polar GaN, enabling the remote homoepitaxy of N-polar GaN via MOCVD. Comparative analysis of N- and Ga-polar GaN substrates reveals different outcomes, attributed to the polarity-dependent thermochemical stability of graphene on GaN substrate. Evidence from spectroscopy and microscopy supports the pronounced thermochemical stability of graphene on N-polar GaN. Molecular dynamics simulations confirm the dependence of graphene's thermochemical stability on GaN polarity. The practical application of the study is demonstrated in the fabrication of flexible light-emitting diodes.
Article
Chemistry, Physical
Razia, Manjusha Chugh, Madhav Ranganathan
Summary: This study introduces a method to calculate the surface energy of clean surfaces by separating the contributions of the pseudo-hydrogen layer, and proposes a modified plane stress condition suitable for slabs with a passivated bottom layer. It is found that the unreconstructed surface exhibits compressive stress, which is relieved through surface reconstructions.
APPLIED SURFACE SCIENCE
(2021)
Article
Nanoscience & Nanotechnology
Takashi Matsumae, Yuichi Kurashima, Hideki Takagi, Yusuke Shirayanagi, Shuichi Hiza, Kunihiko Nishimura, Eiji Higurashi
Summary: A new method was developed to bond GaN and diamond substrates using an atomically thin bonding layer at room temperature, which effectively prevents physical damage to diamond crystals caused by sputtering, potentially facilitating high-power and high-frequency operation of GaN devices.
SCRIPTA MATERIALIA
(2022)
Review
Chemistry, Physical
Joana C. Mendes, Michael Liehr, Changhui Li
Summary: This paper discusses in detail the potential and technical challenges of integrating synthetic diamond with high thermal conductivity and electric breakdown strength with gallium nitride, as well as the advantages and disadvantages of different methods.
Article
Engineering, Electrical & Electronic
Joon Sang Kang, Man Li, Huan Wu, Huuduy Nguyen, Toshihiro Aoki, Yongjie Hu
Summary: Thermal management is crucial in electronic systems, and the integration of novel semiconductor materials like boron arsenide and boron phosphide with other materials such as gallium nitride can significantly improve cooling performance and reduce hot-spot temperatures in high-electron-mobility transistors.
NATURE ELECTRONICS
(2021)
Article
Engineering, Electrical & Electronic
Rohith Soman, Maliha Noshin, Srabanti Chowdhury
Summary: Lateral N-polar GaN devices have shown better performance than Ga-polar GaN counterparts in mm-wave applications. This study focuses on the growth conditions for a vertical N-polar GaN device stack, aiming to improve the output power density. The results show that higher growth temperature and NH3 flow rate contribute to increased structural quality, while also causing an increase in surface roughness. The optimized sample exhibited excellent structural quality and low oxygen and carbon concentration, and showed a low screw dislocation density on the sapphire substrate.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2022)
Article
Chemistry, Multidisciplinary
Mohamadali Malakoutian, Xiang Zheng, Kelly Woo, Rohith Soman, Anna Kasperovich, James Pomeroy, Martin Kuball, Srabanti Chowdhury
Summary: The increasing power density in electronics applications leads to Joule heating and high temperature in the device channel, which affects performance and reliability. This study demonstrates the possibility of growing high-quality diamond at 400 degrees C, which can be integrated with various semiconductors and offers high thermal conductivity and low thermal boundary resistance.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Engineering, Electrical & Electronic
Seungbin Jeong, Kwangjae Lee, Jaeyi Chun, Rohith Soman, Srabanti Chowdhury
Summary: GaN vertical FinFETs on a bulk GaN substrate were fabricated and their self-heating and DC-RF dispersion were investigated. The devices showed high drain current density and low gate leakage with low-temperature post-gate processes. The specific on-resistance was one of the lowest values reported, and low dispersion was observed for devices away from the wafer edge. The influence of self-heating was more significant as the fin width scaled down or the number of fingers increased.
IEEE ELECTRON DEVICE LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Rafael Perez Martinez, David J. Munzer, Bhawani Shankar, Boris Murmann, Srabanti Chowdhury
Summary: There is a significant disconnect between the linearity metrics used by device and circuit engineers in GaN technology, which degrades its maximum performance. A detailed linearity analysis is conducted on four different GaN device variants using derivative superposition (DS) method to evaluate amplifier performance under modulated conditions. Conventional linearity metrics at the device level, such as output third-order intercept point (OIP3) and output 1-dB compression point (OP1 dB), are compared with communication standard-based metrics, including adjacent channel power ratio (ACPR) and error vector magnitude (EVM), to provide best practices for quantifying power amplifier (PA) linearity. The study reveals that employing more devices primarily improves the input-bias range of the device, not the peak amplifier performance under modulation. This work provides device engineers with a circuit-level perspective on linearity to enhance RF performance for practical deployment.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Editorial Material
Materials Science, Multidisciplinary
Grace Xing, Zetian Mi, Srabanti Chowdhury
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2023)
Article
Crystallography
Xinyi Wen, Kwang Jae Lee, Yusuke Nakazato, Jaeyi Chun, Srabanti Chowdhury
Summary: For the first time, a low-temperature GaN (LT-GaN) layer prepared by MOCVD regrowth was used as a Mg stopping layer (MSL) for a GaN trench CAVET with p-GaN as a CBL. The MSL effectively suppresses Mg out-diffusion into the regrown AlGaN/GaN channel, enhancing the current capability of the GaN vertical devices. The study investigates the influence of MSL regrowth temperature and thickness on device performance and demonstrates that LT-GaN as the MSL is a promising approach for isolating Mg from subsequent layers in GaN vertical devices with a Mg-doped p-type layer.
Article
Physics, Applied
Maliha Noshin, Xinyi Wen, Rohith Soman, Xiaoqing Xu, Srabanti Chowdhury
Summary: In this study, N-polar AlGaN channel HEMT structures with varying Al mole fraction were grown using MOCVD. The high-quality morphology and Al composition of the structures were confirmed using atomic force microscopy and x-ray diffraction spectra. The results showed a decreasing trend in mobility with increasing Al mole fraction, which can be attributed to a combination of alloy-scattering and optical phonon-scattering mechanisms. HEMTs fabricated from these structures exhibited a drain current of 320 mA/mm for a 4 μm long-channel device.
APPLIED PHYSICS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Maliha Noshin, Rohith Soman, Srabanti Chowdhury
Summary: Devices made from ultrawide bandgap materials are being widely investigated for high-power and RF electronics. Nitrogen-polar GaN channel HEMTs exhibit better performance compared to their metal-polar counterparts. In this work, the first experimental demonstration of N-polar all-AlGaN HEMT devices with different Al compositions (20% and 30%) in the channel is reported. These devices showed high drive current, low leakage current, large on/off ratio, and high breakdown voltage without field plate structures.
IEEE ELECTRON DEVICE LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Sudip K. Mazumder, Lars F. Voss, Karen M. Dowling, Adam Conway, David Hall, Robert J. Kaplar, Gregory W. Pickrell, Jack Flicker, Andrew T. Binder, Srabanti Chowdhury, Victor Veliadis, Fang Luo, Sameh Khalil, Thomas Aichinger, Sandeep R. Bahl, Matteo Meneghini, Alain B. Charles
Summary: This article provides an overview of power semiconductor devices (PSDs) for the distributed energy resource (DER) system. It begins with an introduction to electrically triggered silicon carbide (SiC) and gallium nitride (GaN) devices, followed by a brief explanation of ultrawide bandgap (UWBG) PSDs. Additionally, it discusses optically activated PSDs such as photoconductive semiconductor switches (PCSS) and optical bipolar PSDs, and concludes with an overview of PSD packaging and reliability considerations.
IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS
(2023)
Proceedings Paper
Computer Science, Interdisciplinary Applications
Rafael Perez Martinez, Masaya Iwamoto, Jianjun Xu, Philipp Pahl, Srabanti Chowdhury
Summary: This paper compares the accuracy and attributes of different FET models in the context of GaN HEMT modeling. Three FET models implemented within PathWave Advanced Design System are compared, with a focus on analyzing the use of neural networks for modeling I-V and Q-V relations. The models are validated and benchmarked using data from a specific GaN-on-SiC HEMT, showing the power of neural network technology for accurately modeling thermal and trapping effects of GaN HEMTs.
2023 IEEE RADIO FREQUENCY INTEGRATED CIRCUITS SYMPOSIUM, RFIC
(2023)
Proceedings Paper
Engineering, Electrical & Electronic
Yuke Cao, James W. Pomeroy, Jingshan Wang, Patrick Fay, Bhawani Shankar, Srabanti Chowdhury, Martin Kuball
Summary: Semiconductor device developments are guided by simulations and comparing measured and simulated IV curves is a common method to assess device performance. However, the problem of low breakdown voltage due to different implantation or doping levels lacks guidance for mitigation. We present a technique based on EFISHG to directly measure electric strength in vertical GaN-on-GaN pn junctions with submicron resolution, which aids in improving device design and reducing product development cycles.
GALLIUM NITRIDE MATERIALS AND DEVICES XVIII
(2023)
Article
Materials Science, Multidisciplinary
Mohamadali Malakoutian, Rohith Soman, Kelly Woo, Srabanti Chowdhury
Summary: The increasing power demands of electronic applications, including 5G/6G, have made thermal management crucial. Enhancing heat transfer using thermally conductive materials like diamond is important to address the performance degradation and early failure caused by Joule heating in the device channel due to higher power. Diamond integration onto the device's top, near the channel, can be achieved through direct chemical vapor deposition.
Proceedings Paper
Computer Science, Artificial Intelligence
Dennis Rich, Anna Kasperovich, Mohamadali Malakoutian, Robert M. Radway, Shiho Hagiwara, Takahide Yoshikawa, Srabanti Chowdhury, Subhasish Mitra
2023 60TH ACM/IEEE DESIGN AUTOMATION CONFERENCE, DAC
(2023)
