Article
Chemistry, Multidisciplinary
Xiaoman Zhang, Wangwang Xu, W. J. Meng, Andrew C. Meng
Summary: This study successfully grew high-quality single crystal AlScN nanowires through ultra-high vacuum reactive sputtering technique and characterized their structure and properties. The nanowires exhibit significantly reduced mosaic spread and predominantly single ferroelectric domains, as well as a high piezoelectric constant.
Article
Computer Science, Information Systems
Peipei Ma, Jun Zheng, Yabao Zhang, Zhi Liu, Yuhua Zuo, Buwen Cheng
Summary: Heavy doped n-type beta-Ga2O3 (HD-Ga2O3) was obtained by Si ion implantation on unintentionally doped beta-Ga2O3 single crystal substrates. The ion-implanted layer showed high lattice quality after high-temperature annealing, and the minimum specific contact resistance was reduced by the formation of titanium oxide at the Ti/Ga2O3 interface. Lateral beta-Ga2O3 diodes prepared using HD-Ga2O3 exhibited high forward current density and low specific on-resistance.
TSINGHUA SCIENCE AND TECHNOLOGY
(2023)
Article
Physics, Applied
Niklas Wolff, Simon Fichtner, Benedikt Haas, Md Redwanul Islam, Florian Niekiel, Maximilian Kessel, Oliver Ambacher, Christoph Koch, Bernhard Wagner, Fabian Lofink, Lorenz Kienle
Summary: This study presents atomic-scale evidence for ferroelectric polarization inversion in a wurtzite-type material using epitaxial Al0.75Sc0.25N thin films. The electric field-induced formation of Al-polar inversion domains in the originally N-polar film is confirmed by atomic resolution imaging and anisotropic etching. The epitaxial relationship of the sapphire/AlN/Mo/AlScN multilayer stack is discussed with results from electron diffraction experiments and XRD pole figures.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Chemistry, Physical
Chunqing Ma, Bosung Kim, Dong-Ho Kang, Sang-Woo Kim, Nam-Gyu Park
Summary: A nonchemical charge transfer doping approach is used to continuously tune the work function of perovskite, leading to improved conductivity. Positive and negative applied voltages result in n- and p-type charge transfer doping, respectively, enhancing carrier mobility and density. This tunable work function offers insights into innovative exploitation of perovskite materials in optoelectronic devices.
ACS ENERGY LETTERS
(2021)
Article
Physics, Applied
Yunfei He, Shangyi Chen, Merrilyn Mercy Adzo Fiagbenu, Chloe Leblanc, Pariasadat Musavigharavi, Gwangwoo Kim, Xingyu Du, Jiazheng Chen, Xiwen Liu, Eric A. Stach, Roy H. Olsson, Deep Jariwala
Summary: This letter presents the oriented growth and switching of thin ferroelectric aluminum scandium nitride (AlScN) films directly on degenerately doped 4H silicon carbide (SiC) wafers. The high-quality thin Al0.68Sc0.32N films on doped SiC substrates enable the monolithic integration of nonvolatile memory with SiC-based logic devices suitable for high temperature operation as well as high-power switching, memory, and sensing applications.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Dhruba Das, Asokan Kandasami, M. S. Ramachandra Rao
Summary: This study reports the formation of n-type ultrananocrystalline diamond through phosphorus ion implantation, with high electrical conductivity. Raman study confirms the restoration of crystallinity after high-temperature annealing. Varying the fluence allowed for obtaining a lower thermal activation energy and high carrier concentration, while Hall measurements revealed a two band conduction mechanism in the phosphorus-implanted diamond.
APPLIED PHYSICS LETTERS
(2021)
Article
Chemistry, Physical
Xiaoman Zhang, Eric A. Stach, W. J. Meng, Andrew C. Meng
Summary: In this study, epitaxial wurtzite AlScN thin films were grown on Si (111) substrates by ultra-high vacuum reactive sputtering. Sc alloying in AlN enhances piezoelectricity and induces ferroelectricity, making epitaxial thin films suitable for systematic investigations of these materials. Increasing Sc concentration leads to crystalline disorder and a structural transition from wurtzite to rocksalt, as well as nanoscale compositional segregation consistent with spinodal decomposition. The observed composition fluctuations are correlated with polarization domains, suggesting an influence on ferroelectric properties. These results provide a route for creating single crystal AlScN films and self-assembled composition modulation.
NANOSCALE HORIZONS
(2023)
Article
Engineering, Electrical & Electronic
Mingyo Park, Jialin Wang, Azadeh Ansari
Summary: This study presents the first demonstration of thin-film ferroelectric Aluminum Scandium Nitride (AlScN)-on-silicon composite resonators, achieving high-overtone resonance modes with a high figure of merit (FoM). The research shows that the addition of a passive Si device layer underneath the thin piezo-stack results in improved quality factor (Q), structural robustness, and overall FoM. High k(t)(2) values and FoM are reported for the TE resonant frequency, showing a significant improvement compared to the co-fabricated AlScN-only FBARs.
IEEE ELECTRON DEVICE LETTERS
(2021)
Article
Nanoscience & Nanotechnology
Ding Wang, Ping Wang, Shubham Mondal, Subhajit Mohanty, Tao Ma, Elaheh Ahmadi, Zetian Mi
Summary: This paper reports on the resistive switching behavior and memory effect in an ultrawide-bandgap ferroelectric ScAlN/GaN heterostructure. The structure exhibits stable ON and OFF states that last for months at room temperature, and shows stable operation at high temperatures close to or even above the Curie temperature. The underlying mechanism is directly related to charge reconstruction induced by the ferroelectric field effect at the hetero-interface. The polar heterostructure demonstrates robust resistive switching landscape and electrical polarization engineering capability, and has the potential to integrate with both silicon and GaN technologies, enabling a wide range of multifunctional applications.
ADVANCED ELECTRONIC MATERIALS
(2022)
Article
Multidisciplinary Sciences
Jing Wang, Jing Ma, Houbing Huang, Ji Ma, Hasnain Mehdi Jafri, Yuanyuan Fan, Huayu Yang, Yue Wang, Mingfeng Chen, Di Liu, Jinxing Zhang, Yuan-Hua Lin, Long-Qing Chen, Di Yi, Ce-Wen Nan
Summary: The authors propose programmable logic gates and circuits based on electric-field controllable conductive domain walls, demonstrating stable and repeatable on-and-off switching of conductive domain walls through reversible transformations. This research shows potential applications in logic processing.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Physical
Adriano Panepinto, Arnaud Krumpmann, David Cornil, Jerome Cornil, Rony Snyders
Summary: The study found that ion implantation can transform nitrogen-doped TiO2 material into an efficient hole transport layer, reducing electron-hole recombination processes and allowing for control over optical and electrical properties.
APPLIED SURFACE SCIENCE
(2021)
Article
Materials Science, Multidisciplinary
Vytautas Kavaliunas, Yoshinori Hatanaka, Yoichiro Neo, Giedrius Laukaitis, Hidenori Mimura
Summary: The conduction band discontinuity between n-type Si substrates and anatase TiO2 films was investigated using XPS and energy band diagram analysis, revealing accurate values for different dopant concentrations. Temperature-dependent I-V characteristics and light transmittance measurements were used to evaluate the electronic properties of TiO2 films, leading to a proposed band diagram for the n-type Si/TiO2 heterojunction.
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2021)
Article
Nanoscience & Nanotechnology
Tae Yoon Lee, Myeong Seop Song, Jung Woo Cho, In Hyeok Choi, Chihwan An, Jong Seok Lee, Seung Chul Chae
Summary: By studying Al0.66Sc0.34N thin films, the remarkable reliability and large ferroelectricity of the material are demonstrated. This study provides potential possibilities for the application of ferroelectric materials in neuromorphic computing.
ADVANCED ELECTRONIC MATERIALS
(2023)
Article
Physics, Applied
Seunguk Song, Kwan-Ho Kim, Srikrishna Chakravarthi, Zirun Han, Gwangwoo Kim, Kyung Yeol Ma, Hyeon Suk Shin, Roy H. Olsson, Deep Jariwala
Summary: This study presents a MoS2 negative capacitance FET based on AlScN ferroelectric material. By including a non-ferroelectric dielectric layer in the gate stack, the hysteresis behavior of the NCFET can be minimized, demonstrating excellent transport characteristics.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Sung-Lin Tsai, Takuya Hoshii, Hitoshi Wakabayashi, Kazuo Tsutsui, Tien-Kan Chung, Edward Y. Chang, Kuniyuki Kakushima
Summary: The crystallographic characteristics and ferroelectric properties of 50nm-thick sputter-deposited Al0.78Sc0.22N films deposited at room temperature and 400 degrees C were investigated. It was found that the films grew in the c-axis direction and exhibited poling-free ferroelectric properties. Despite low switching cycle endurance, metal-ferroelectric-metal capacitors showed high remnant polarization suitable for different deposition temperatures.
APPLIED PHYSICS LETTERS
(2021)
Article
Physics, Applied
Haruki Tanigawa, Kentaro Matsuura, Iriya Muneta, Takuya Hoshii, Kuniyuki Kakushima, Kazuo Tsutsui, Hitoshi Wakabayashi
JAPANESE JOURNAL OF APPLIED PHYSICS
(2020)
Article
Physics, Applied
Jinhan Song, Y. Lin, T. Hoshii, H. Wakabayashi, K. Tsutsui, K. Kakushima
JAPANESE JOURNAL OF APPLIED PHYSICS
(2020)
Article
Physics, Applied
Jinhan Song, Atsuhiro Ohta, Takuya Hoshii, Hitoshi Wakabayashi, Kazuo Tsutsui, Kuniyuki Kakushima
Summary: Enhanced oxidation of 4H-SiC surface was achieved in an oxygen-lean environment using a thin CeOx layer. By capping the CeOx layer with a SiO2 layer, high peak field mobility and a threshold voltage higher than 2 V were obtained, showing advantages over other gate oxide formation processes.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
Sung-Lin Tsai, Takuya Hoshii, Hitoshi Wakabayashi, Kazuo Tsutsui, Tien-Kan Chung, Edward Y. Chang, Kuniyuki Kakushima
Summary: The crystallographic characteristics and ferroelectric properties of 50nm-thick sputter-deposited Al0.78Sc0.22N films deposited at room temperature and 400 degrees C were investigated. It was found that the films grew in the c-axis direction and exhibited poling-free ferroelectric properties. Despite low switching cycle endurance, metal-ferroelectric-metal capacitors showed high remnant polarization suitable for different deposition temperatures.
APPLIED PHYSICS LETTERS
(2021)
Editorial Material
Physics, Applied
Sung-Lin Tsai, Takuya Hoshii, Hitoshi Wakabayashi, Kazuo Tsutsui, Tien-Kan Chung, Edward Y. Chang, Kuniyuki Kakushima
APPLIED PHYSICS LETTERS
(2021)
Article
Physics, Applied
Junji Kataoka, Sung-Lin Tsai, Takuya Hoshii, Hitoshi Wakabayashi, Kazuo Tsutsui, Kuniyuki Kakushima
Summary: Research on 50 nm thick ferroelectric Al0.78Sc0.22N films with TiN electrodes revealed that the leakage current gradually shifted during initial switching, stabilizing at a specific value. This change was interpreted as the formation of a tunneling barrier due to nitrogen vacancies at the metal interface.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
Sung-Lin Tsai, Takuya Hoshii, Hitoshi Wakabayashi, Kazuo Tsutsui, Tien-Kan Chung, Edward Yi Chang, Kuniyuki Kakushima
Summary: The study reveals the significant impact of thickness on the ferroelectric properties of Al0.78Sc0.22N films, with a gradual degradation of remnant polarization below 35 nm. Switching cycle tests show a wake-up effect in the films, especially for thick films.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
Takamasa Kawanago, Takahiro Matsuzaki, Ryosuke Kajikawa, Iriya Muneta, Takuya Hoshii, Kuniyuki Kakushima, Kazuo Tsutsui, Hitoshi Wakabayashi
Summary: This paper presents the device concept for achieving high-gain operation of a tungsten diselenide (WSe2) complementary metal-oxide-semiconductor (CMOS) inverter at a low power supply voltage. The concept involves developing a doping technique and gate stack technology. By spin-coating with a fluoropolymer and poly(vinyl alcohol) (PVA), both electrons and holes can be doped to WSe2. Furthermore, a hybrid self-assembled monolayer/aluminum oxide (AlO(x)) gate dielectric is used to enhance gate capacitance and interfacial properties. The experimental results demonstrate a high gain of 9 at a supply voltage of 0.5V. This study paves the way for the future research and development of devices and circuits based on transition metal dichalcogenides.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Sung-Lin Tsai, Takuya Hoshii, Hitoshi Wakabayashi, Kazuo Tsutsui, Tien-Kan Chung, Edward Yi Chang, Kuniyuki Kakushima
Summary: The effects of field cycling on ferroelectric properties of Al0.78Sc0.22N capacitors were investigated. The research found that in the early switching cycles, the switching voltage decreased, possibly due to the formation of nitrogen-vacancy facilitating atom displacements. Fatigue effect was observed in further switching cycles, especially in domains with low switching voltage. Leakage current analysis showed a continuous reduction in the Schottky barrier height for electrons with increasing number of switching cycles. The breakdown of Al0.78Sc0.22N films was triggered by excessive leakage current causing Joule heat.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Kazuto Mizutani, Takuya Hoshii, Hitoshi Wakabayashi, Kazuo Tsutsui, Edward Y. Chang, Kuniyuki Kakushima
Summary: The effects of a 1 nm thick CeO(x) capping layer on the ferroelectric characteristics of Y-doped HfO2 films were investigated. The results showed that the capping layer shortened the time required to stabilize the ferroelectric phase, increased the remnant polarization, and suppressed the formation of conductive filaments. Therefore, the CeO(x) capping layer is effective in promoting the ferroelectric phase in HfO2 with high switching endurance.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Ryota Shibukawa, Sung-Lin Tsai, Takuya Hoshii, Hitoshi Wakabayashi, Kazuo Tsutsui, Kuniyuki Kakushima
Summary: The sputtering power dependence of 40 nm thick Al0.7Sc0.3N ferroelectric properties was investigated. Higher sputtering power resulted in better orientation growth along the c-axis and improved leakage current and breakdown field. High remnant polarization and low coercive field were achieved, and a wake-up effect was observed.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Si-Meng Chen, Sung-Lin Tsai, Kazuto Mizutani, Takuya Hoshii, Hitoshi Wakabayashi, Kazuo Tsutsui, Edward Yi Chang, Kuniyuki Kakushima
Summary: A method for shifting the threshold voltage (Vth) in GaN high electron mobility transistors using self-upward polarized Al1-xScxN gate dielectrics is proposed. The direction of spontaneous polarization is controlled by inserting an Al2O3 layer. A Vth shift of 8 V is achieved by changing the polarization direction. The thickness scaling in the Al1-xScxN layer shows a linear relationship to Vth, indicating a high spontaneous polarization. With the combination of a recess process, it is feasible to achieve a high positive Vth for enhancement-mode operation.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
M. Nishizawa, T. Hoshii, H. Wakabayashi, K. Tsutsui, Y. Daigo, I Mizushima, T. Yoda, K. Kakushima
Summary: This paper proposes a method for using device simulation to extract the hole lifetime of a thin n-type SiC epitaxial layer. By correlating the voltage drop across a forward-biased pn diode and parallel pn diodes at the same current density with the defined hole lifetime, the hole lifetime can be extracted. It was found that there was a severe error in the extraction of the voltage drop, which was attributed to surface recombination. The introduction of a field-plate between the anodes recovered the extraction error, achieving an extraction accuracy of 99% even with a high surface recombination velocity.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Atsuki Miyata, T. Hoshii, H. Wakabayashi, K. Tsutsui, K. Kakushima
Summary: This paper investigates a photodetector based on an AlGaN/GaN high electron mobility transistor on Si, which exhibits long decay time after removal of light irradiation, making it unsuitable for applications requiring fast response. The decay time is successfully suppressed from 75 to 2 seconds by modulating the substrate voltage.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
