Article
Nanoscience & Nanotechnology
Seonyeong Kim, Dong Hoon Shin, Yong-Sung Kim, In-Ho Lee, Chang-Won Lee, Sunae Seo, Suyong Jung
Summary: The energy band alignments and material properties at the contacts between metal and 2D semiconducting transition metal dichalcogenide films are essential for electronic and optical device applications. Vertical diodes with asymmetric metal-SCTMD contact areas were used to study contact-limited charge flows in tunneling and emission transport regimes. The experimental and analytical approaches demonstrated in this research provide a powerful tool for evaluating metal-SCTMD contacts qualitatively and quantitatively.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Chemistry, Physical
Zixuan Zhao, Can Zou, E. Zhou, Qing Liu, Kai Chen, Xingfu Wang, Longfei He, Fangliang Gao, Shuti Li
Summary: Interface engineering improves the performance of graphene-based photodetectors. A graphene/GaAs heterojunction photodetector was fabricated and by inserting an Al2O3 tunneling layer, its performance was enhanced through direct tunneling (DT) and Fowler-Nordheim tunneling (FNT). The thickness of the tunneling layer was found to significantly affect the photodetector's performance. Compared with a graphene/GaAs photodetector, the graphene/Al2O3(2 nm)/GaAs photodetector showed improved responsivity, detectivity, and external quantum efficiency, achieving values of 0.80 A/W, 3.02 x 1011 Jones, and 306% respectively under 1 mW/cm2 light intensity at 2 V bias. The photodetector also exhibited a fast response with rise/decay times of 3 ms/8.6 ms. The improved performance of the photodetector was mainly attributed to the effective modification of the interface state by the Al2O3 tunneling layer and the influence of the two tunneling mechanisms based on DT and FNT.
SURFACES AND INTERFACES
(2023)
Article
Chemistry, Multidisciplinary
Luke W. Smith, Jack O. Batey, Jack A. Alexander-Webber, Yu-Chiang Hsieh, Shin- Fung, Tom Albrow-Owen, Harvey E. Beere, Oliver J. Burton, Stephan Hofmann, David A. Ritchie, Michael Kelly, Tse-Ming Chen, Hannah J. Joyce, Charles G. Smith
Summary: This study investigates the insulating states in monolayer graphene grown by chemical vapor deposition (CVD) and wet transferred on Al2O3 without specialized fabrication techniques. The results show the existence of insulating properties and the opening of an energy gap induced by the magnetic field in a graphene device with a bottleneck. A locally high-quality region within the bottleneck dominates transport and causes the device to behave as an insulating tunnel junction. The use of wet transfer fabrication techniques and multiplexing demonstrates the convenience of these scalable and reasonably simple methods for finding high-quality devices for fundamental physics research and functional properties.
Article
Chemistry, Physical
Chulho Park, Juchan Lee, Min Jeong Kim, Ngoc Thanh Duong, Mun Seok Jeong, Seong Chu Lim
Summary: Investigations into the diode behaviors of MoTe2 and ReS2 heterostructures revealed a crossover between thermionic emission and Fowler-Nordheim tunneling for carrier injection mechanisms. Experimental and theoretical analyses demonstrated that carrier injection can be controlled by modulating the potential barrier height, temperature, and applied strength. This study expands our understanding of charge transport mechanisms in staggered TMD heterojunctions.
APPLIED SURFACE SCIENCE
(2021)
Article
Physics, Multidisciplinary
Mehrnegar Aghayan, Pouya Valizadeh
Summary: This study investigates the reverse gate-leakage current of AlGaN/GaN heterojunction field-effect transistors (HFETs) realized on array of submicron sized fins and conventional mesa isolation feature geometries at room temperature and zero drain-source bias. The significance of leakage from the top surface gate as well as gated etched GaN surfaces, especially sidewalls, is studied for a wide range of gate-source voltages (V-GS). It is found that leakage through the gated GaN surfaces, particularly the sidewalls, is more significant than the leakage from the top surface gate in the explored fin-type HFETs, while the sidewall leakage is of importance only at less negative values of V-GS in the mesa category. The dominance of leakage paths at different V-GS values is attributed to the stronger electric field across the barrier in the gated region of the mesa-type HFET.
Article
Chemistry, Multidisciplinary
Zongqi Bai, Yang Xiao, Qing Luo, Miaomiao Li, Gang Peng, Zhihong Zhu, Fang Luo, Mengjian Zhu, Shiqiao Qin, Kostya Novoselov
Summary: The emergence of two-dimensional materials has led to important applications in electronic and optoelectronic devices. However, there are limitations such as low ON/OFF ratio and Schottky barrier formation. In this study, highly tunable field-effect tunneling transistors based on vertical graphene-WS2-graphene heterostructures were demonstrated, overcoming these limitations and achieving low off-state current, high ON/OFF ratio, and controllable carrier transport polarity.
Article
Nanoscience & Nanotechnology
Inchul Choi, Nae Bong Jeong, Minjeong Kim, Jaeho Yu, Hyun-Jong Chung
Summary: The current mechanism of the graphene-WS2 junction evolves from thermionic emission to field emission as the height decreases with the accumulation of electrons, and also changes with increasing temperature due to the decrease in WS2 thickness. The alignment of the Fermi level of graphene to the Dirac point may cause a kink in the I-D-V-D curves.
ADVANCED ELECTRONIC MATERIALS
(2022)
Article
Engineering, Electrical & Electronic
Marco Turchetti, Yujia Yang, Mina Bionta, Alberto Nardi, Luca Daniel, Karl K. Berggren, Phillip D. Keathley
Summary: Recent advancements in nanofabrication have enabled the creation of vacuum electronic devices with nanoscale free-space gaps. These nanoelectronic devices promise the benefits of cold-field emission and transport through free space, while reducing the device footprint, increasing operating bandwidth, and reducing power consumption. However, the interplay between different electron emission mechanisms from these devices is not well understood.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Chemistry, Physical
Jun -Dar Hwang, Cyuan-Sin Li, Chin -Yang Chang
Summary: With the development of MIS field-effect transistors, the use of MgO/SiOx stack dielectrics can effectively suppress the gate leakage current and improve the performance of MIS diodes. The stack reduces the oxygen vacancy of MgO, decreases the fixed oxide charge and interface trap charge density, and enhances the rectification ratio. The barrier height also increases in the stack, allowing for Fowler-Nordheim tunneling at high reverse-bias voltage and direct tunneling at low reverse-bias voltages.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Nanoscience & Nanotechnology
Masahiro Nakayama, Kentaro Kajimoto, Tomoki Misaka, Naoya Mishima, Takashi Yamada, Hiroshi Ohoyama, Takuya Matsumoto
Summary: The alignment of molecular electronic levels in a molecular multilayer is crucial for desired functions. This study utilized a new testing method to probe the energy-level alignment in an organic multilayer. The results showed weak coupling between layers at low voltage and significant loss of electrostatic energy at high voltage.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Computer Science, Information Systems
Giorgiana-Catalina Ilie (chiranu), Cristian Tudoran, Otilia Neagoe, Florin Draghici, Gheorghe Brezeanu
Summary: This paper describes a nonvolatile switch based on n-type floating-gate transistors, where switch states are programmed through memory cell floating-gate voltage. The advantages include higher levels than the application supply, reduced power consumption, and on-state resistance not depending on supply voltage, making it suitable for low-voltage applications.
Article
Chemistry, Physical
Qing Liu, Weidong Song, Xingfu Wang, Zixuan Zhao, Can Zhou, Kai Chen, Shaobing Zhan, Fangliang Gao, Shuti Li
Summary: This study reports a quantum mechanical Fowler-Nordheim tunneling (FNT) mechanism in a graphene 2D/GaN 3D ultraviolet (UV) photodetector with an atomic layer deposition Al2O3 tunneling layer, and investigates the conversion between direct tunneling (DT) and FNT. Under reverse bias (< -0.253 V), the high-speed photogenerated carriers overcome the thin insulator layer through FNT, resulting in impact ionization and multiplication of photocurrent. The photodetector exhibits excellent photoresponse performances under weak light conditions, including high responsivity (122.57 A/W), ultrahigh specific detectivity (5.63 x 10(14) Jones), and high sensitivity (1.29 x 10(7)%), indicating its exceptional weak light detection ability. This work presents a novel approach to fabricate high-performance optoelectronic devices utilizing the FNT tunneling mechanism.
Article
Multidisciplinary Sciences
Lei Tong, Meng Peng, Peisong Wu, Xinyu Huang, Zheng Li, Zhuiri Peng, Runfeng Lin, Qiaodong Sun, Yaxi Shen, Xuefeng Zhu, Peng Wang, Jianbin Xu, Lei Ye
Summary: The research utilizes MoTe2/h-BN/MoTe2/h-BN heterostructure to achieve hole-dominated Fowler-Nordheim quantum tunneling transport in both on and off states, achieving high detectivity and fast response in photodetection performance, promising superior imaging capabilities.
Article
Nanoscience & Nanotechnology
Maryam Sadat Amiri Naeini, Pierre Berini
Summary: Plasmonic hot carriers on metal-oxide-semiconductor (MOS) diodes have the potential for innovative optoelectronics on technologically important structures. The photoresponse of MOS diodes is reported due to the tunneling of hot holes created in the metal contact via the absorption of infrared surface plasmons. The theoretical modeling and measurements show excellent agreement, allowing for the extraction of tunneling effective masses in the oxide of the MOS structures.
Article
Nanoscience & Nanotechnology
Dong Hoon Shin, Duk Hyun Lee, Sang-Jun Choi, Seonyeong Kim, Hakseong Kim, Kenji Watanabe, Takashi Taniguchi, Eleanor E. B. Campbell, Sang Wook Lee, Suyong Jung
Summary: Weak interlayer couplings at 2D van der Waals interfaces fundamentally distinguish out-of-plane charge flow, the information carrier in vdW-assembled vertical electronic and optical devices, from the in-plane band transport processes. The out-of-plane charge transport behavior in 2D van der Waals semiconducting transition metal dichalcogenides (SCTMD) is studied and it is found that Fowler-Nordheim tunneling becomes the dominant quantum transport process in ultrathin SCTMDs, down to monolayers, in the high electric field regime, especially at low temperatures. The sequential layer-by-layer FN tunneling is observed to dominate the charge flow in few-layer SCTMDs, providing insight into the Fermi level positions and layer numbers of the SCTMD films.
ADVANCED ELECTRONIC MATERIALS
(2023)
