Article
Materials Science, Multidisciplinary
X. Cui, K. Ji, L. Liu, W. Sha, B. Wang, N. Xu, Q. Hua, W. Hu
Summary: High electron mobility transistors (HEMTs) based on AlGaN/GaN heterojunctions hold great promise for high-performance power electronics. By introducing high-kappa gate dielectric, such as HfZrOx (HZO), to form MOS-HEMTs, the performance of HEMTs can be enhanced, including higher output performance, lower leakage current, and improved surface properties. Furthermore, the piezotronic effect, which combines piezoelectric and semiconductor properties, offers a novel approach for optimizing HEMTs through external stress. In this study, the dynamic piezotronic effect of AlGaN/GaN HEMTs with HZO gate dielectric is investigated in pulse voltage modes. The results show that applying tensile stress to the GaN layer leads to decreased DC and pulse output characteristics of the MOS-HEMTs, as well as a slight increase in gate leakage current. Theoretical analysis suggests that the applied tensile stress effectively improves the energy band height of the triangular potential well and affects the energy states of defects. This work not only inspires the modulation of device performance using dynamic piezotronic effect, but also expands the potential applications of HEMTs in strain-controlled platforms.
MATERIALS TODAY PHYSICS
(2022)
Article
Chemistry, Physical
Dmitri S. S. Arteev, Alexei V. V. Sakharov, Wsevolod V. V. Lundin, Evgenii E. E. Zavarin, Andrey E. E. Nikolaev, Andrey F. F. Tsatsulnikov, Viktor M. M. Ustinov
Summary: This study investigates the influence of Fe segregation on the electrical properties of two-dimensional electron gas in AlGaN/AlN/GaN heterostructures. It was found that the concentration and mobility of the electron gas decrease with thinner channel layer thickness, leading to an increase in sheet resistance. The drop in mobility is attributed to a combination of ionized impurity scattering and various scattering effects.
Article
Engineering, Electrical & Electronic
Jiarui Guo, Yan Gu, Yushen Liu, Fangzhou Liang, Wei Chen, Feng Xie, Xifeng Yang, Weiying Qian, Xiangyang Zhang, Guoqing Chen, Guofeng Yang
Summary: This study designs a UV photodetector that utilizes a two-dimensional electron gas at the AlGaN/GaN interface with an AlGaN symmetrical interdigital structure. The AlGaN interdigital structure is fabricated with a Ti/Al/Ti/Au metal stack for ohmic contacts. The interdigital AlGaN/GaN heterostructure enhances the polarization electric field in the GaN absorption layer, facilitating the separation and transport of photogenerated carriers. The polarization-enhanced physical mechanism of the AlGaN/GaN 2DEG UV PD is explored through theoretical simulations. The designed UV PD exhibits a broadband characteristic with a response spectra from 300 to 365 nm and a cutoff wavelength of 365 nm, matching the bandgap wavelength of GaN. The normalized photocurrent-to-dark current ratio (NPDR) of 1.31 x 10(9) W-1 is measured at 10 V.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Nanoscience & Nanotechnology
Guangyuan Jiang, Yuanjie Lv, Zhaojun Lin, Yongxiong Yang, Yang Liu
Summary: In this study, the impact of Al composition on additional polarization charges and 2DEG density in AlGaN/GaN heterostructure HFETs was investigated. It was found that increasing Al composition in the barrier layer leads to higher additional polarization charges and 2DEG density, but due to the higher density of 2DEG, the scattering effect of additional polarization charges on 2DEG is weaker.
PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES
(2021)
Article
Nanoscience & Nanotechnology
A. Filatova-Zalewska, Z. Litwicki, K. Moszak, W. Olszewski, K. Opolczynska, D. Pucicki, J. Serafinczuk, D. Hommel, A. Jezowski
Summary: High thermal conductivity is crucial for nitride-based power electronic and deep-UV light emitters. In this study, in-plane and cross-plane thermal conductivity of AlGaN/GaN superlattices were measured, showing differences in thermal behavior with changing period thickness and temperature. The Callaway method was used for thermal conductivity calculation, taking into account the dependence of boundary scattering rate on phonon wavelength.
Article
Engineering, Electrical & Electronic
Md. Abdul Kaium Khan, Mohammad Abdul Alim, Christophe Gaquiere
Summary: Analysis of the temperature dependency of 2DEG in AlGaN/GaN HEMT and AlGaN/InGaN/GaN pHEMT reveals a decreasing trend in 2DEG density in both devices, with a higher reduction rate observed in AlGaN/GaN HEMT. The incorporation of an additional 5 nm thick pseudomorphic layer of InGaN in AlGaN/InGaN/GaN pHEMT improves 2DEG transport properties and enhances transistor performance. Overall, AlGaN/InGaN/GaN pHEMT demonstrates better 2DEG stability with temperature compared to AlGaN/GaN HEMT.
MICROELECTRONIC ENGINEERING
(2021)
Article
Chemistry, Inorganic & Nuclear
J. Mani, S. Radha, R. Rajkumar, L. Preethi, Manimuthu Veerappan, M. Arivanandhan, G. Anbalagan
Summary: Quaternary copper-based thermoelectric materials are promising alternatives to current efficient thermoelectric materials. Cu2-xCoxNiSnS4 samples (0 ≤ x ≤ 0.1) were synthesized using the solvothermal method. The addition of Co resulted in a cubic crystal structure with a decreasing energy bandgap. The Co-doped Cu2NiSnS4 showed a garland-like flower structure composed of nanosheets. The Seebeck coefficient increased with increasing Co content, and the CC-4 sample exhibited a high power factor and a minimal thermal conductivity.
JOURNAL OF SOLID STATE CHEMISTRY
(2023)
Article
Engineering, Electrical & Electronic
Jie Li, Min Tang, Junfa Mao
Summary: An analytical thermal model is proposed in this article, which accurately predicts the temperature rise of AlGaN/GaN high-electron-mobility transistors (HEMTs) and estimates the thermal coupling between gate fingers in multifinger devices.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
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
Physics, Applied
Xiaowen Tang, Xiaoli Lu, ZheZhe Cong, Zekun Shi, Dangpo Wang, Jianing Li, Xiaohua Ma, Yue Hao
Summary: This study characterized the modulation of the 2DEG in the AlGaN/GaN heterostructure induced by ferroelectric domains using microscopic and local transport measurement techniques. The results provide direct evidence for effective ferroelectric domain engineering in GaN HEMTs, and a prototype device was fabricated to demonstrate gate control using the polarization of the ferroelectric domain. This approach offers a promising solution for the contradiction between the 2DEG density and gate controllability in GaN HEMTs, showing great potential for future GaN radio frequency devices.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Analytical
Robert Sokolovskij, Hongze Zheng, Wenmao Li, Guangnan Zhou, Qing Wang, Guoqi Zhang, Hongyu Yu
Summary: The particulate matter micro-sensor for automotive exhaust systems based on a gateless wide-bandgap AlGaN/GaN high electron mobility transistor was developed and tested. The sensor showed good sensitivity towards soot and fast response time, with successful regeneration post-soot deposition indicating high temperature stability and harsh environment operation compatibility. However, further optimization is needed to mitigate high-temperature interdiffusion.
SENSORS AND ACTUATORS B-CHEMICAL
(2021)
Article
Engineering, Electrical & Electronic
Yuebo Liu, Wanqing Yao, Honghui Liu, Longkun Yang, Shangfeng Liu, Liuyun Yang, Fengge Wang, Yuan Ren, Junyu Shen, Minjie Zhang, Zhisheng Wu, Yang Liu, Qi Wang, Xinqiang Wang, Baijun Zhang
Summary: This study focuses on reducing the series resistance of Schottky barrier diodes (SBD) by vertically stacking multiple AlGaN/GaN heterojunctions, resulting in a significant improvement in cutoff frequency to 16 GHz in the millimeter-wave band. The utilization of a half through-hole structure for the Schottky electrode also helps achieve a low capacitance, contributing to the overall performance enhancement. By forming multiple parallel 2DEG channels, the SBDs demonstrate a significant decrease in series resistance, with the quintuple-channel SBD showing only 39.5% of the single-channel SBD's resistance.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2021)
Article
Physics, Applied
Hong-Quan Nguyen, Thanh Nguyen, Philip Tanner, Tuan-Khoa Nguyen, Abu Riduan Md Foisal, Jarred Fastier-Wooller, Tuan-Hung Nguyen, Hoang-Phuong Phan, Nam-Trung Nguyen, Dzung Viet Dao
Summary: The study demonstrates the effect of stress or strain on the electronic characteristics of a normally off AlGaN/GaN HEMT and its potential as a highly sensitive pressure sensor with a strain sensitivity of 1250ppm(-1).
The change in drain current is most pronounced when the gate bias is near-threshold and the drain bias is slightly larger than the saturation bias.
APPLIED PHYSICS LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Kavita T. Upadhyay, Manju K. Chattopadhyay
Summary: This paper provides a review of significant research work in the field of GaN-based sensor technologies, including classification of existing work, explanation of sensor sensing mechanisms, as well as the challenges and future opportunities facing current sensing systems.
MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS
(2021)
Article
Engineering, Electrical & Electronic
C. Bryan, P. Faucherand, M. Charles, M. Plissonnier, G. Savelli
Summary: The study demonstrates the stable thermoelectric properties of both n-type GaN and AlGaN/GaN heterostructure, making them suitable for high-performance thermoelectric sensors.
JOURNAL OF ELECTRONIC MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Timothy D. Brown, Stephanie M. Bohaichuk, Mahnaz Islam, Suhas Kumar, Eric Pop, R. Stanley Williams
Summary: This study presents a model of VO2/SiN Mott threshold switches constructed using the principle of local activity. The model is refined to measurable material properties by considering a minimal set of quasistatic and dynamic electrical and thermal data. It accurately predicts electrical and thermal conductivities and capacitances, as well as locally active dynamics.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Physical
Zhou Li, Chen Liu, Jessica Jane Frick, Adrian K. Davey, Matthew N. Dods, Carlo Carraro, Debbie G. Senesky, Roya Maboudian
Summary: This work presents the synthesis, characterization, and absorption capacity of graphene aerogel loaded with UiO-66-NH2 metal organic framework (MOF). The density-tunable MOF/GA composites were synthesized by adjusting the mass ratio of MOF to graphene oxide (GO) in the starting solution. Scanning electron microscopy (SEM) images and pore size calculations showed that MOF loading affected the macroporous structure of the GA framework but not the mesoporous structure. The MOF loading exhibited minimum density for the 10-30% samples. MOF-30%/GA demonstrated the highest absorption capacity for chloroform among all solvents tested.
Article
Engineering, Electrical & Electronic
Cagil Koroglu, Eric Pop
Summary: As physical transistor scaling nears its limits and memory bandwidth becomes a bottleneck for many applications, three-dimensional (3D) integration offers a promising solution to continue Moore's law. Effective thermal management is essential to maximize the performance benefits of 3D integrated circuits (ICs), and using high thermal conductivity insulators like AlN and hBN can significantly reduce thermal resistance and overcome thermal challenges. In addition, highly anisotropic insulators such as hBN can be utilized as heat spreaders in memory-on-logic architectures to keep both memory and logic dies cool.
IEEE ELECTRON DEVICE LETTERS
(2023)
Article
Multidisciplinary Sciences
Weisheng Li, Xiaoshu Gong, Zhihao Yu, Liang Ma, Wenjie Sun, Si Gao, Cagil Koroglu, Wenfeng Wang, Lei Liu, Taotao Li, Hongkai Ning, Dongxu Fan, Yifei Xu, Xuecou Tu, Tao Xu, Litao Sun, Wenhui Wang, Junpeng Lu, Zhenhua Ni, Jia Li, Xidong Duan, Peng Wang, Yuefeng Nie, Hao Qiu, Yi Shi, Eric Pop, Jinlan Wang, Xinran Wang
Summary: By hybridizing with semi-metallic antimony (0112) through strong van der Waals interactions, the electrical contact of monolayer molybdenum disulfide is improved, meeting the requirements for the development of next-generation electronics.
Article
Chemistry, Multidisciplinary
Victoria Chen, Hye Ryoung Lee, Cagil Koroglu, Connor J. McClellan, Alwin Daus, Eric Pop
Summary: In this study, we characterized the electrical and thermoelectric properties of layered WSe2 with thicknesses ranging from 10 to 96 nm at temperatures between 300 and 400 K. By electrostatically gating the devices with an ion gel, we were able to investigate both electron and hole behavior over a wide range of carrier densities. The highest n- and p-type Seebeck coefficients for thin-film WSe2 at room temperature, -500 and 950 μV/K respectively, were obtained in this study. We also highlighted the significance of low substrate thermal conductivity for lateral thermoelectric measurements, which improves the platform for future studies on other nanomaterials.
Article
Chemistry, Multidisciplinary
Jie Zhao, Asir Intisar Khan, Mikhail Y. Efremov, Zichao Ye, Xiangjin Wu, Kangsik Kim, Zonghoon Lee, H. -S. Philip Wong, Eric Pop, Leslie H. Allen
Summary: The phase transition of Sb2Te3/Ge2Sb2Te5 superlattices was studied using nanocalorimetry, providing insights into the thermodynamics of superlattice-based PCM and enabling low-power switching.
Article
Physics, Applied
Stephanie M. Bohaichuk, Suhas Kumar, Mahnaz Islam, Miguel Munoz Rojo, R. Stanley Williams, Gregory Pitner, Jaewoo Jeong, Mahesh G. Samant, Stuart S. P. Parkin, Eric Pop
Summary: Oscillatory devices are important in biomimetic neuronal spiking computing systems, but understanding their time scales is challenging due to the influence of external circuitry. In this study, we demonstrate the challenges using a sub-100-nm VO2 Mott oscillator with a nanogap cut in a metallic carbon nanotube electrode. Despite its nanoscale thermal volume, external parasitics result in orders-of-magnitude slower dynamics. We discuss methods for determining when measurements are dominated by extrinsic factors and the conditions for observing intrinsic oscillation frequencies.
PHYSICAL REVIEW APPLIED
(2023)
Article
Nanoscience & Nanotechnology
Emanuel Ber, Ryan W. Grady, Eric Pop, Eilam Yalon
Summary: Achieving good electrical contacts is a major challenge in devices based on atomically thin 2D semiconductors. This study experimentally examines the classical transmission line model description of contacts to 2D materials and proposes a modification based on an additional lateral resistance component. It finds that the additional lateral resistance component dominates the contact resistance in atomically thin semiconductor devices and is responsible for the back-gate bias and temperature dependence.
ADVANCED ELECTRONIC MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
Il-Kwon Oh, Asir Intisar Khan, Shengjun Qin, Yujin Lee, H. -S. Philip Wong, Eric Pop, Stacey F. Bent
Summary: This study explores the application of area-selective atomic layer deposition (AS-ALD) technique in the fabrication of RRAM devices and finds that AS-ALD can improve the reliability and accuracy of RRAM, regardless of device size. The application of this technique will contribute to the improvement of other data storage technologies.
ACS APPLIED MATERIALS & INTERFACES
(2023)
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
Optics
Qitong Li, Jung-Hwan Song, Fenghao Xu, Jorik van de Groep, Jiho Hong, Alwin Daus, Yan Joe Lee, Amalya C. Johnson, Eric Pop, Fang Liu, Mark L. Brongersma
Summary: A general pathway to reduce the detrimental impact of dephasing and non-radiative decay processes in quantum devices is illustrated through photonic design of device electrodes. The design enables large Purcell enhancement, convenient electrical gating, and high modulation efficiencies.
Article
Multidisciplinary Sciences
Joel Martis, Sandhya Susarla, Archith Rayabharam, Cong Su, Timothy Paule, Philipp Pelz, Cassandra Huff, Xintong Xu, Hao-Kun Li, Marc Jaikissoon, Victoria Chen, Eric Pop, Krishna Saraswat, Alex Zettl, Narayana R. Aluru, Ramamoorthy Ramesh, Peter Ercius, Arun Majumdar
Summary: Four-dimensional scanning transmission electron microscopy (4D-STEM) was used to determine the electron charge density in monolayer MoS2 by combining center of mass (CoM) images and annular dark field (ADF) images. The contribution of core electrons and valence electrons to the charge density was evaluated, with the core electrons mainly responsible for the spatial modulation and the valence electrons forming a featureless background. This study highlights the importance of probe shape in interpreting charge densities derived from 4D-STEM and suggests the need for smaller electron probes.
NATURE COMMUNICATIONS
(2023)
Article
Nanoscience & Nanotechnology
Aviv Schwarz, Hadas Alon-Yehezkel, Adi Levi, Rajesh Kumar Yadav, Koushik Majhi, Yael Tzuriel, Lauren Hoang, Connor S. Bailey, Thomas Brumme, Andrew J. Mannix, Hagai Cohen, Eilam Yalon, Thomas Heine, Eric Pop, Ori Cheshnovsky, Doron Naveh
Summary: Recent research on 2D transition metal dichalcogenides (TMDCs) has led to important discoveries in fundamental phenomena and device applications. In this study, a two-step treatment with organic molecules was used to heal native defects in CVD-grown WSe2 and WS2. The adsorption of thiols was found to only partially passivate defects, but molecular trimming and release of atomic sulfur significantly improved semiconductor quality. Time-dependent XPS and first-principles calculations were used to characterize defects and their healing.
NPJ 2D MATERIALS AND APPLICATIONS
(2023)
Article
Chemistry, Multidisciplinary
Timm Swoboda, Nicolas Wainstein, Sanchit Deshmukh, Cagil Koroglu, Xing Gao, Mario Lanza, Hans Hilgenkamp, Eric Pop, Eilam Yalon, Miguel Munoz Rojo
Summary: Heat dissipation is a major concern for electronic devices, especially at the nanoscale. Scanning thermal microscopy (SThM) is a versatile tool for measuring device temperature with nanoscale resolution but quantifying thermal features is challenging. This study calibrates a thermo-resistive SThM probe using metal lines of different widths and evaluates its sensitivity under different conditions. The results provide new insights for accurately determining the temperature of scanned devices.
Article
Materials Science, Multidisciplinary
Hon-Loen Sinn, Aravindh Kumar, Eric Pop, Akm Newaz
Summary: Researchers demonstrated a bismuth-1L-MoS2-bismuth device with ohmic electrical contacts and extraordinary optoelectronic properties by suppressing metal-induced gap states (MIGS) at the metal-monolayer MoS2 interface. This overcomes Fermi-level pinning and expands the application range of optoelectronic devices based on 2D transition metal dichalcogenides.
ADVANCED PHOTONICS RESEARCH
(2023)