Article
Nanoscience & Nanotechnology
Mingzhu Pei, Qingshun Dong, Minhuan Wang, Yudi Wang, Hongru Ma, Jing Liu, Ruiting Wang, Jiming Bian, Yantao Shi
Summary: Interfacial passivation engineering is crucial for the development of perovskite solar cells. By tuning the interplanar spacing of the passivation layer, researchers have found that reducing the spacing can improve the hole tunneling efficiency and enhance the overall passivation effect.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Physics, Applied
Renzhou Zheng, Jingbin Lu, Yu Wang, Lei Liang, Yugang Zeng, Li Qin, Yongyi Chen, Xue Zhang, Ziyi Chen, Xiaoyi Li, Xinxu Yuan, Yumin Liu
Summary: This study demonstrates the use of AlGaAs hole/electron transport layers to enhance the performance of GaAs-based betavoltaic batteries. The output performance of batteries is predicted and optimized using Monte Carlo codes and COMSOL Multiphysics. Experimental results show that the optimized battery structure achieves high current density, voltage, and power density. Temperature tests also reveal the relationship between battery performance and temperature.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
Article
Green & Sustainable Science & Technology
Waldemar Kaiser, Lakshmi N. S. Murthy, Chin-Lung Chung, Ken-Tsang Wong, Julia W. P. Hsu, Alessio Gagliardi
Summary: In this study, the mechanisms of photocurrent in dilute donor organic solar cells (OSCs) were analyzed using kinetic Monte Carlo (kMC) simulations, with a focus on hole back transfer and long-range hopping. The research found that hole back transfer can explain the concentration dependences of photocurrents and the Jsc dependence on light intensity.
ADVANCED ENERGY AND SUSTAINABILITY RESEARCH
(2021)
Article
Chemistry, Physical
Hansung Kim, Gunwu Ju, Seung-Hwan Kim, Kiyoung Lee, Myoungho Jeong, Hyun Cheol Koo, Hyung-jun Kim
Summary: The study utilized interdiffusion between epitaxial Ge layers and GaAs substrates to control the doping concentration and type of the Ge layers, achieving extremely high n-type doping concentration in a Ge layer grown at low temperature. Subsequent annealing processes led to a decrease in doping concentration and an n- to p-type transition due to differences in diffusivity between As and Ga atoms.
SURFACES AND INTERFACES
(2021)
Article
Chemistry, Multidisciplinary
Mikhail O. Petrushkov, Demid S. Abramkin, Eugeny A. Emelyanov, Mikhail A. Putyato, Oleg S. Komkov, Dmitrii D. Firsov, Andrey V. Vasev, Mikhail Yu. Yesin, Askhat K. Bakarov, Ivan D. Loshkarev, Anton K. Gutakovskii, Victor V. Atuchin, Valery V. Preobrazhenskii
Summary: This study investigates the use of low-temperature GaAs layers as dislocation filters in GaAs/Si heterostructures. The results show that the introduction of LT-GaAs layers and post-growth cyclic annealing significantly improve the quality of GaAs layers, reducing the dislocation density and surface roughness.
Article
Materials Science, Multidisciplinary
M. N. Bataev, M. A. Chukeev, M. M. Sharipova, P. A. Belov, P. S. Grigoryev, E. S. Khramtsov, I. Ignatiev, S. A. Eliseev, V. A. Lovtcius, Yu. P. Efimov
Summary: This paper presents a comprehensive study of both light-hole and heavy-hole excitons in quantum wells, focusing on their energy positions and interactions with light. The findings show that the corrections to the exciton energy due to mixing are small, and the oscillator strength of light-hole excitons is significantly lower than that of heavy-hole excitons. This research is important for understanding the characteristics of excitons in semiconductor materials.
Article
Physics, Applied
Justin C. Goodrich, Chee-Keong Tan, Damir Borovac, Nelson Tansu
Summary: Efficient p-type doping of III-nitride materials is challenging, but the use of dilute-anion III-nitride materials can significantly increase activation efficiency, reduce ionization energy, and enhance p-type conductivity compared to conventional nitrides.
APPLIED PHYSICS LETTERS
(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
Thilo Hepp, Julian Veletas, Robin Guenkel, Oliver Massmeyer, Johannes Glowatzki, Wolfgang Stolz, Sangam Chatterjee, Kerstin Volz
Summary: GaAs-based semiconductor laser diodes with strained type-I quantum wells offer advantages of energy efficiency, superior performance, and long-term reliability in the near-infrared spectral range. Alloys containing nitrogen and bismuth show potential for extending emission wavelengths towards telecommunication bands, but challenges in incorporating these elements with reasonable material quality have led to the exploration of alternate approaches. By embedding a Ga(As,Bi) quantum well between two Ga(N,As) quantum wells in a W-type quantum well heterostructure, significant optical gain can be achieved, paving the way for tailored WQWs with even longer emission wavelengths.
CRYSTAL GROWTH & DESIGN
(2021)
Article
Astronomy & Astrophysics
Usman A. Gillani, Jamil Ahmed, Mudassar Rehman
Summary: This work presents Hawking radiation as a quantum tunneling phenomenon from accelerating BTZ black holes. The Hawking radiation from the horizon of the accelerating BTZ black hole for Dirac particles is calculated using the WKB approximation for the Dirac equation in the background of three-dimensional black holes. The tunneling probability obtained from this procedure is used to calculate the Hawking temperature of the background three-dimensional black hole. The study is consistent with previous research in the absence of the acceleration parameter, and quantum corrections to the Hawking temperature of the accelerating BTZ black hole are also investigated.
Article
Chemistry, Physical
Nicholas M. Randell, Renaud Miclette Lamarche, Franceso Tintori, Roman Chernikov, Gregory C. Welch, Simon Trudel
Summary: The study reports the fabrication of amorphous aCuOx thin films using a UV-based thin-film deposition method from commercially available starting materials, which exhibit p-type semiconductor behavior after thermal annealing and can be used as HTLs in organic photovoltaic devices.
ACS APPLIED ENERGY MATERIALS
(2021)
Article
Materials Science, Multidisciplinary
Sapir Bitton, Nir Tessler
Summary: Theoretical studies have traditionally focused on ion migration within the perovskite layer, but emerging experimental evidence suggests ions can also migrate into blocking layers, impacting device degradation. Simulation results show good agreement with experimental data, indicating ion accumulation at the electrode interface as a key factor in device dynamics. Additionally, migration into blocking layers is found to significantly influence the device energy level diagram and can potentially alter the perovskites into p or n type solar cells.
JOURNAL OF MATERIALS CHEMISTRY C
(2021)
Article
Nanoscience & Nanotechnology
Thais Chagas, Guilherme A. S. Ribeiro, Barbara L. T. Rosa, Danial Bahrami, Arman Davtyan, Rafael R. Barreto, Juan C. Gonzalez, Rogerio Magalhaes-Paniago, Angelo Malachias
Summary: In this study, the researchers investigated the structural and electronic properties of Mg-doped GaAs(111) nanowires, revealing conducting Ga2Mg/Mg clusters on the lateral surfaces, enabling electrical contacts with reduced Schottky barriers. Density functional theory was used to investigate the electronic response of Ga2Mg, showing metallic behavior at room temperature and quantum confinement at low temperatures.
ACS APPLIED NANO MATERIALS
(2021)
Article
Physics, Condensed Matter
Mohammed Rida Qasem, Farid Falyouni, Fatima-Zahra Elamri, Driss Bria
Summary: In this article, we study the existence and behavior of electronic states located in the band gap of Multi-Quantum Wells (MQWs) disturbed by two layers of defects. We use the formalism of the interface response theory to investigate the transmission and energy level variation. The position, thickness, and concentration of Al in the two defective layers play a crucial role in increasing electronic states.
PHYSICA B-CONDENSED MATTER
(2023)
Article
Chemistry, Multidisciplinary
Shiyun Lei, Yuanyuan Xiao, Kanglin Yu, Biao Xiao, Ming Wan, Liyong Zou, Qingliang You, Renqiang Yang
Summary: This study investigates the hole injection mechanism in quantum dot light-emitting diodes (QLEDs) through a combination of experiments and simulations. It reveals that applied bias reduces the barrier height, facilitating hole injection and confining electrons within the quantum dots. The research also demonstrates that thermally assisted tunneling is the predominant pathway for hole injection. This study is significant for understanding the hole injection mechanism in QLEDs.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Physics, Multidisciplinary
Md Shafayat Hossain, Tongzhou Zhao, Songyang Pu, M. A. Mueed, M. K. Ma, K. A. Villegas Rosales, Y. J. Chung, L. N. Pfeiffer, K. W. West, K. W. Baldwin, J. K. Jain, M. Shayegan
Summary: Composite fermions in a clean two-dimensional electron gas can be tuned to very low densities to form a Bloch ferromagnet, with an abrupt transition to full magnetization similar to Bloch ferromagnetism observed experimentally. By measuring the Fermi wavevector, a sudden transition from partially spin-polarized to fully spin-polarized ground state was observed as the density of composite fermions decreases. Theoretical calculations considering Landau level mixing provide a semi-quantitative explanation of this phenomenon.
Article
Chemistry, Physical
Yoon Jang Chung, K. A. Villegas Rosales, K. W. Baldwin, P. T. Madathil, K. W. West, M. Shayegan, L. N. Pfeiffer
Summary: By improving sample quality and innovating materials and vacuum chamber design, researchers have achieved a breakthrough in GaAs quantum well systems with two-dimensional electrons, demonstrating high mobility and low residual impurities.
Article
Physics, Multidisciplinary
Md S. Hossain, M. K. Ma, K. A. Villegas-Rosales, Y. J. Chung, L. N. Pfeiffer, K. W. West, K. W. Baldwin, M. Shayegan
Summary: This study demonstrates the ability to control valley polarization in a two-dimensional electron system through gate bias, explaining that the phenomenon arises from electron-electron interaction. Furthermore, the researchers found that the valley polarization transition is accompanied by a sudden change in sample resistance, which is of interest for potential valleytronic transistor device applications.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
Yoon Jang Chung, D. Graf, L. W. Engel, K. A. Villegas Rosales, P. T. Madathil, K. W. Baldwin, K. W. West, L. N. Pfeiffer, M. Shayegan
Summary: This study investigates the ground state of two-dimensional electron systems (2DESs) at low Landau level filling factors using improved experimental methods. It confirms the existence of fractional quantum Hall states that comply with the Jain sequence even in the extremely low Landau level filling limit.
PHYSICAL REVIEW LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Yoon Jang Chung, C. Wang, S. K. Singh, A. Gupta, K. W. Baldwin, K. W. West, M. Shayegan, L. N. Pfeiffer, R. Winkler
Summary: This paper reports the fabrication of ultra-high-quality (001) GaAs 2D hole systems with significantly improved mobility values. High-order fractional quantum Hall states and a deep minimum in the magnetoresistance were observed in the measurements.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Physics, Multidisciplinary
Md. S. Hossain, M. K. Ma, K. A. Villegas-Rosales, Y. J. Chung, L. N. Pfeiffer, K. W. West, K. W. Baldwin, M. Shayegan
Summary: The interplay between the Fermi sea anisotropy, electron-electron interaction, and localization phenomena can give rise to exotic many-body phases. This study reports the observation of an ordered anisotropic Wigner solid in a clean two-dimensional electron system with anisotropic effective mass and Fermi sea.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Chengyu Wang, A. Gupta, S. K. Singh, Y. J. Chung, L. N. Pfeiffer, K. W. West, K. W. Baldwin, R. Winkler, M. Shayegan
Summary: In this study, a new and unexpected even-denominator FQHS was observed in a high-quality GaAs 2D hole system at filling factor v = 3/4. This FQHS is observed in the lowest Landau level and exhibits non-Abelian characteristics.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Meng K. Ma, Chengyu Wang, Y. J. Chung, L. N. Pfeiffer, K. W. West, K. W. Baldwin, R. Winkler, M. Shayegan
Summary: By tuning the position of the crossing between the two lowest-energy Landau levels in a low-density two-dimensional hole system, a ferromagnetic quantum Hall ground state with skyrmion excitations is observed. The energy gap for the quantum Hall state remains exceptionally large and only shows a small dip near the crossing, indicating a robust quantum Hall ferromagnet as the ground state.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Md. Shafayat Hossain, Meng K. Ma, Y. J. Chung, S. K. Singh, A. Gupta, K. W. West, K. W. Baldwin, L. N. Pfeiffer, R. Winkler, M. Shayegan
Summary: We report the observation of a 1/2 fractional quantum Hall state in a high-quality two-dimensional electron system. The properties of this state can be controlled by applying strain and changing the magnetic field, allowing for phase transitions and tunability.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
P. T. Madathil, K. A. Villegas Rosales, C. T. Tai, Y. J. Chung, L. N. Pfeiffer, K. W. West, K. W. Baldwin, M. Shayegan
Summary: Disorder-induced localization in condensed matter physics and the temperature dependence of plateau-to-plateau transitions in quantum Hall systems have been extensively studied. In this study, scaling measurements were performed in the fractional quantum Hall state regime, where electron-electron interaction dominates. The results suggest that the critical exponent for transitions between different fractional quantum Hall states varies and is close to the one reported for transitions between high-order fractional quantum Hall states with intermediate strength. The nonuniversal nature of the observed critical exponent is discussed.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
Zijin Lei, Erik Cheah, Filip Krizek, Thomas Bahler, Peter Marki, Werner Wegscheider, Mansour Shayegan, Thomas Ihn, Klaus Ensslin
Summary: Quantum transport measurements were conducted in undoped InSb quantum wells with high-quality, gate-defined two-dimensional hole and electron systems. The carrier systems in both polarities exhibited tunable spin-orbit interactions, as determined through weak antilocalization measurements. The effective mass of InSb holes increased significantly with carrier density, as evidenced by the temperature dependence of Shubnikov-de Haas oscillations. Coincidence measurements in a tilted magnetic field were used to estimate the spin susceptibility of the InSb two-dimensional hole system, which showed a rapid decrease in the g factor with increasing carrier density.
PHYSICAL REVIEW RESEARCH
(2023)
Article
Materials Science, Multidisciplinary
Md Shafayat Hossain, Meng K. Ma, Y. J. Chung, S. K. Singh, A. Gupta, K. W. West, K. W. Baldwin, L. N. Pfeiffer, R. Winkler, M. Shayegan
Summary: This study demonstrates how the valley degree of freedom impacts the fractional quantum states (FQHSs) through magnetotransport experiments. The researchers find a surprisingly robust ferromagnetism of the FQHSs and the underlying composite fermions (CFs), suggesting a strong interaction between the CFs in the system.
Article
Materials Science, Multidisciplinary
Yoon Jang Chung, A. Gupta, K. W. Baldwin, K. W. West, M. Shayegan, L. N. Pfeiffer
Summary: Ultrahigh-mobility GaAs two-dimensional electron systems (2DESs) have been a significant platform for condensed-matter physics research for several decades. Continuous improvement in sample quality has enabled scattering-free transport and led to the emergence of exotic many-body phenomena. Recent research shows the potential for further increasing the mobility limit of GaAs 2DESs, and discusses scenarios for achieving mobility values exceeding 100 x 10(6) cm(2)/Vs.
Article
Materials Science, Multidisciplinary
K. A. Villegas Rosales, P. T. Madathil, Y. J. Chung, L. N. Pfeiffer, K. W. West, K. W. Baldwin, M. Shayegan
Summary: Composite fermions (CFs), formed by pairing an electron and an even number of magnetic flux quanta, are exotic quasiparticles that emerge in an interacting electron system at high magnetic fields. They can explain phenomena such as fractional quantum Hall state and other many-body phases. This study presents experimental measurements of the effective mass of CFs in GaAs quantum wells of varying thickness, revealing a relationship between mass and energy gap. Comparisons with theoretical calculations show significant discrepancies, indicating the need for more accurate calculations to explain the experimental data.
Article
Materials Science, Multidisciplinary
K. A. Villegas Rosales, S. K. Singh, H. Deng, Y. J. Chung, L. N. Pfeiffer, K. W. West, K. W. Baldwin, M. Shayegan
Summary: A low-disorder, two-dimensional electron system subjected to a large perpendicular magnetic field and cooled to very low temperatures provides a rich platform for studies of many-body quantum phases. The study investigates the screening properties of bubble phases and the penetration of electric fields at different temperatures in this system. The bubbles formed at very low temperatures poorly screen the electric field due to being pinned by the residual disorder potential, allowing a large electric field to reach the top gate.