Article
Crystallography
Polyxeni Chatzopoulou, Isaak G. Vasileiadis, Philomela Komninou, Vassilis Pontikis, Theodoros Karakostas, George P. Dimitrakopulos
Summary: The use of strained substrates can overcome indium incorporation limits without causing plastic relaxation in InGaN quantum wells, which is particularly important for short-period InGaN/GaN superlattices. Elastic strain in these heterostructures modifies their optoelectronic behavior. Density functional theory calculations were used to investigate the band-gap energy variation in short-period InGaN/GaN superlattices with one monolayer thick pseudomorphic quantum wells. Heterostructures with equibiaxially strained GaN barriers were compared to those with relaxed barriers. The study reveals a reduction of the band gap with lower indium contents, attributed to the influence of highly strained nitrogen sublattice. However, above mid-range indium compositions, the band gap increases with indium content due to the reduction of compressive strain in quantum wells caused by the tensile strain of barriers. Indium clustering induced by phase separation was considered as another modifier, but it was found to have no significant influence on the band gap. Overall, this study provides important insights into the behavior of band-gap energy in strained superlattices, optimizing the performance of optoelectronic devices based on InGaN/GaN heterostructures.
Article
Physics, Condensed Matter
I Gorczyca, G. Staszczak, G. Targowski, E. Grzanka, J. Smalc-Koziorowska, T. Suski, T. Kawamura, Y. Kangawa
Summary: The use of superlattices of InxGa1-xN/InyGa1-yN type allows for more precise tuning of emission energy and shifting light emission to lower energies. This approach can overcome the technological problem of low In incorporation in InGaN based heterostructures.
SUPERLATTICES AND MICROSTRUCTURES
(2021)
Article
Physics, Applied
A. A. Ivanov, V. V. Chaldyshev, E. E. Zavarin, A. V. Sakharov, W. V. Lundin, A. F. Tsatsulnikov
Summary: In this study, we experimentally demonstrate the formation of a superradiant optical mode in a resonant Bragg structure at room temperature. The mode is characterized by an increase in amplitude and a change in shape of the resonant optical reflection due to the electromagnetic coupling of the excitons. Using optical modeling, we evaluate the broadening parameters of the excitonic states in GaN quantum wells.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Valery Davydov, Evgenii Roginskii, Yuri Kitaev, Alexander Smirnov, Ilya Eliseyev, Dmitrii Nechaev, Valentin Jmerik, Mikhail Smirnov
Summary: Experimental and theoretical studies were conducted on phonon modes in GaN/AlN superlattices, with results showing good agreement between calculations and experimental data, opening up new possibilities for analyzing structural characteristics using Raman spectroscopy and optimizing growth technologies.
Article
Chemistry, Physical
Grzegorz Staszczak, Iza Gorczyca, Ewa Grzanka, Julita Smalc-Koziorowska, Grzegorz Targowski, Tadeusz Suski
Summary: To achieve red emission in nitride quantum structures, the low In incorporation in InGaN-based heterostructures needs to be addressed. By changing the superlattice parameters and the composition of the buffer structures, the light emission can be shifted to lower energies.
Article
Crystallography
Athith Krishna, Aditya Raj, Nirupam Hatui, Stacia Keller, Umesh K. Mishra
Summary: The shortcomings in acceptors of p-type III-nitride semiconductors have resulted in limited research on p-channel electronic devices. This study experimentally demonstrates the presence of acceptor-like traps in Ga-polar p-type uniformly doped (AlGaN/AlN)/GaN SLs with limited Mg doping, acting as the primary source of holes.
Article
Chemistry, Multidisciplinary
Valery Davydov, Evgenii M. Roginskii, Yuri Kitaev, Alexander Smirnov, Ilya Eliseyev, Eugene Zavarin, Wsevolod Lundin, Dmitrii Nechaev, Valentin Jmerik, Mikhail Smirnov, Markus Pristovsek, Tatiana Shubina
Summary: This study reveals that interface interdiffusion between GaN and AlN layers in short-period GaN/AlN superlattices has an effect on the Raman spectrum, with bands related to A(1)(LO) confined phonons being particularly sensitive. The correlation between Raman spectra and interface quality offers new possibilities for analyzing the structural characteristics of these superlattices.
Article
Computer Science, Information Systems
Yangfeng Li, Yang Jiang, Haiqiang Jia, Wenxin Wang, Rong Yang, Hong Chen
Summary: This study numerically investigates the optical and electronic performances of InGaN LEDs in the green gap range with Ga- and N-polar. The results show that N-polar LEDs have higher light-output power and lower turn-on voltage compared to Ga-LEDs, indicating a promising realization of high luminous efficiency InGaN LEDs in the green gap range.
Article
Engineering, Chemical
Min Zhang, Yunyuan Dong, Mengling Peng, Xiaobin Chen, Qifu Zheng, Jianming Liao, Wei Chen
Summary: Construction of carbon-based heterostructural photocatalyst materials with high electron transfer rates is an effective strategy for organic pollutant mineralization and toxic metal ion removal under visible-light irradiation. This study developed a facile hydrothermal route to prepare a series of heterojunction photocatalysts, which exhibited excellent photocatalytic activity for degradation of tetracycline hydrochloride and reduction of Cr(VI). Notably, the photocatalysts showed good activity and stability even after cycle experiment. This study provides new insights into the design of carbon-based heterojunction photocatalysts for the removal of harmful chemicals.
SEPARATION AND PURIFICATION TECHNOLOGY
(2023)
Article
Optics
Ondrej Zapadlik, Jan Pejchal, Fedor Levchenko, Romana Kucerkova, Alena Beitlerova, Vojtech Vanecek, Karel Jurek, Martin Nikl
Summary: The scintillation, luminescence, and optical properties of different compositions of Ce-doped Gd3Sc2Ga(2+x)Al(1-x)O12 and Gd2.957Sc1.905Ga(2.138+x)Al(1-x)O12, as well as Mg2+ co-doped Gd3Sc2Ga2.75Al0.25O12:Ce single crystals, were studied. The scintillation efficiency and afterglow were affected by the content of Ga and Sc in the host material. Codoping with Mg2+ improved afterglow but reduced light yield compared to pure Ce-doped samples.
JOURNAL OF LUMINESCENCE
(2023)
Article
Chemistry, Multidisciplinary
Alfred J. H. Jones, Lene Gammelgaard, Mikkel O. Sauer, Deepnarayan Biswas, Roland J. Koch, Chris Jozwiak, Eli Rotenberg, Aaron Bostwick, Kenji Watanabe, Takashi Taniguchi, Cory R. . Dean, Antti-Pekka Jauho, Peter Boggild, Thomas G. Pedersen, Bjarke S. Jessen, Soren Ulstrup
Summary: This work demonstrates the controllable induction of massive Dirac fermions in a graphene device by lithographically patterning superstructures of nanoscale holes. The band dispersion of these fermions is visualized using angle-resolved photoemission spectroscopy with nanoscale spatial resolution, showing a linear scaling of effective mass with feature sizes. Electrostatic doping enhances the effective hole mass and leads to the observation of an electronic band gap, which is strongly renormalized by carrier-induced screening. This methodology allows for the engineering of band structures of massive Dirac quasiparticles at the nanoscale.
Article
Engineering, Electrical & Electronic
Feng-Xian Jiang, Gui-Zhi Zhang, Li-Fei Ji, Ling-Mei Zhao, Xiao-Hong Xu
Summary: ZnO films co-doped with Cr and N were successfully fabricated and characterized in terms of their structure and optical properties. It was found that the electrical and optical characteristics of the films can be tuned by doping with Cr and N, but excessive Cr doping degrades the crystal quality of the films.
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
(2022)
Article
Materials Science, Ceramics
Dongwen Gao, Li Wang, Xueqiong Su
Summary: This study investigates the influence of different doping ratios on the composition, structure, morphology, and luminescence properties of bulk ceramics, determining the optimum doping ratio in this range. The research enhances the optical performance of the material, suggesting improved microstructural, optical, and electrical properties for potential use in new optoelectronic devices.
CERAMICS INTERNATIONAL
(2021)
Article
Chemistry, Physical
Reza Behjatmanesh-Ardakani
Summary: This study investigated the electronic properties of N-doped TiO2 nanotubes using first-principle calculations. The results showed that a 2 ML (8,8) nanotube is a suitable candidate for photocatalyst due to its band gap and formation energy. Unlike the N-doped rutile and anatase phases, there is no electron-hole recombination center in the N-doped 2 ML (8,8) TiO2 nanotube.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Engineering, Electrical & Electronic
Sheng Li, Siyang Liu, Chi Zhang, Le Qian, Chen Ge, Shuxuan Xin, Weifeng Sun, Zhuo Yang, Yuanzheng Zhu, Lihua Ni
Summary: The study found that under repetitive short-circuit stresses, both the gate region and the access region of p-GaN gate high electron mobility transistors are damaged, resulting in shifts in electrical parameters. Moreover, it was observed that the increase in gate leakage current after stress can benefit the switching speed.
IEEE TRANSACTIONS ON POWER ELECTRONICS
(2021)
Article
Optics
K. Pieniak, M. Chlipala, H. Turski, W. Trzeciakowski, G. Muziol, G. Staszczak, A. Kafar, I Makarowa, E. Grzanka, S. Grzanka, C. Skierbiszewski, T. Suski
Summary: This study investigates the impact of injected current on the screening of the built-in electric field in LEDs, revealing that in LEDs with narrow quantum wells, a large portion of built-in field remains even at high injection currents, while in LEDs with wide quantum wells, the electric field is fully screened even at the lowest currents.
Article
Physics, Condensed Matter
I Gorczyca, G. Staszczak, G. Targowski, E. Grzanka, J. Smalc-Koziorowska, T. Suski, T. Kawamura, Y. Kangawa
Summary: The use of superlattices of InxGa1-xN/InyGa1-yN type allows for more precise tuning of emission energy and shifting light emission to lower energies. This approach can overcome the technological problem of low In incorporation in InGaN based heterostructures.
SUPERLATTICES AND MICROSTRUCTURES
(2021)
Article
Chemistry, Physical
Ashfaq Ahmad, Pawel Strak, Kamil Koronski, Pawel Kempisty, Konrad Sakowski, Jacek Piechota, Izabella Grzegory, Aleksandra Wierzbicka, Serhii Kryvyi, Eva Monroy, Agata Kaminska, Stanislaw Krukowski
Summary: This study uses ab initio calculations to determine the polarization difference in III-nitride compounds, showing varying polarization differences between different nitrides. In multi-quantum wells, electric fields are generated by well-barrier polarization difference, and the theoretical results are in good agreement with experimental measurements.
Article
Materials Science, Multidisciplinary
Pawel Strak, Ashfaq Ahmad, Pawel Kempisty, Jacek Piechota, Konrad Sakowski, Grzegorz Nowak, Yoshihiro Kangawa, Jan Lazewski, Stanislaw Krukowski
Summary: Ab initio calculations were used to investigate the physical properties of AlN(0001) surface under Al coverage, revealing the adsorption behavior and energy dependence on coverage for Al adatoms. The adlayer undergoes structural changes from disordered and corrugated to ordered and atomically flat with increasing Al coverage, affecting the Al bonding energy. Thermodynamic analysis identified equilibrium regions with Al vapor, crucial for physical vapor transport AlN growth.
COMPUTATIONAL MATERIALS SCIENCE
(2022)
Article
Materials Science, Multidisciplinary
A. Kafar, A. Sakaki, R. Ishii, K. Shojiki, S. Stanczyk, K. Gibasiewicz, G. Staszczak, L. Marona, D. Schiavon, S. Grzanka, S. Krukowski, T. Suski, P. Perlin, M. Funato, Y. Kawakami
Summary: In this work, we have shown that the structural and emission qualities of high-InN-mole fraction InGaN quantum wells can be improved by increasing the misorientation angle of the substrate.
OPTICAL MATERIALS EXPRESS
(2022)
Article
Optics
J. Slawinska, G. Muziol, M. Siekacz, H. Turski, M. Hajdel, M. Zak, A. Feduniewicz-Zmuda, G. Staszczak, C. Skierbiszewski
Summary: We report on III-nitride-based micro-light-emitting diodes (μLEDs) operating at a wavelength of 450 nm with diameters as small as 2μm. Devices with a standard LED structure followed by a tunnel junction were grown using plasma-assisted molecular beam epitaxy. The emission size of μLEDs was controlled by shallow He implantation of the tunnel junction region. The observed shift of current density for the maximum external quantum efficiency with varying μLED diameter suggests a change in the lateral carrier diffusion in InGaN quantum wells.
Article
Chemistry, Physical
Kamil Koronski, Krzysztof P. Korona, Serhii Kryvyi, Aleksandra Wierzbicka, Kamil Sobczak, Stanislaw Krukowski, Pawel Strak, Eva Monroy, Agata Kaminska
Summary: This paper presents a comparative analysis of the optical properties of non-polar and polar GaN/AlGaN multi-quantum well (MQW) structures using time-resolved photoluminescence (TRPL) and pressure-dependent studies. The results show that the lack of internal electric fields in non-polar structures leads to an improved electron and hole wavefunction overlap, resulting in shorter decay times. On the other hand, polar structures with electric fields exhibit reduced emission energy and wavefunction overlap, leading to a decrease in recombination rate with increasing well width. The study also explores the energy dependence of radiative and non-radiative recombination processes and the influence of electric fields on pressure behavior.
Article
Physics, Applied
Ashfaq Ahmad, Pawel Strak, Pawel Kempisty, Konrad Sakowski, Jacek Piechota, Yoshihiro Kangawa, Izabella Grzegory, Michal Leszczynski, Zbigniew R. Zytkiewicz, Grzegorz Muziol, Eva Monroy, Agata Kaminska, Stanislaw Krukowski
Summary: This work investigates the emergence of polarization doping in AlxGa1-xN layers with graded composition from a theoretical viewpoint. It shows that bulk electric charge density emerges in the graded concentration region and obtains the relation between the polarization bulk charge density and the concentration gradient. The study also demonstrates that a mobile charge appears due to the increase of the distance between opposite polarization-induced charges.
JOURNAL OF APPLIED PHYSICS
(2022)
Correction
Chemistry, Physical
Pawel Strak, Kamil Koronski, Konrad Sakowski, Kamil Sobczak, Jolanta Borysiuk, Krzysztof P. Korona, Piotr A. Drozdz, Ewa Grzanka, Marcin Sarzynski, Andrzej Suchocki, Eva Monroy, Stanislaw Krukowski, Agata Kaminska
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Physics, Applied
Ashfaq Ahmad, Pawel Strak, Konrad Sakowski, Jacek Piechota, Pawel Kempisty, Agata Kaminska, Stanislaw Krukowski
Summary: Ab initio simulations were used to study the properties of GaN/AlN superlattices with different widths for the first time. The results revealed significant differences between polar and nonpolar systems in terms of band diagrams, bandgaps, and oscillator strengths.
JOURNAL OF APPLIED PHYSICS
(2022)
Review
Crystallography
Stanislaw Krukowski, Konrad Sakowski, Pawel Strak, Pawel Kempisty, Jacek Piechota, Izabella Grzegory
Summary: The stability of vicinal surfaces during growth was analyzed, and the mechanism of step coalescence and macrostep formation was determined. The ratio of step density determined the coalescence and formation of macrosteps. Macrosteps were alimented from lower superterrace, and the emission and absorption of single steps sustained the macrostep existence.
PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS
(2022)
Article
Physics, Applied
Abinash Adhikari, Pawel Strak, Piotr Dluzewski, Agata Kaminska, Ewa Przezdziecka
Summary: Semiconductor superlattices have wide applications in the electronic industry. In this study, a short-period superlattice structure composed of CdO and MgO layers was fabricated and its optical properties and pressure dependence of bandgap were investigated. The experimental results were supported by theoretical calculations, providing valuable insight for future optoelectronic applications.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
J. Moneta, G. Staszczak, E. Grzanka, P. Tauzowski, P. Dluzewski, J. Smalc-Koziorowska
Summary: Cross-sectional transmission electron microscopy studies show that a-type dislocations in InGaN/GaN structures deposited along the [0001] direction are post-growth effects caused by stress on lateral surfaces and mechanical processing. Cathodoluminescence mapping reveals the visibility of these defects near the edges of cleaved or polished InGaN/GaN structures. Finite element calculations provide insights into the residual stress distribution near the InGaN/GaN interface at the free edge, and the impact of such defects on device performance is discussed.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Chemistry, Physical
Ashfaq Ahmad, Pawel Strak, Pawel Kempisty, Konrad Sakowski, Jacek Piechota, Yoshihiro Kangawa, Izabella Grzegory, Michal Leszczynski, Zbigniew R. R. Zytkiewicz, Grzegorz Muziol, Eva Monroy, Agata Kaminska, Stanislaw Krukowski
Summary: Polarization doping in a GaN-InN system with a graded composition layer was studied using ab initio simulations. The electric charge volume density in the graded concentration part was determined by spatial potential dependence. The polarization difference in the GaN-InN system was changed by piezoelectric effects and showed potential applications in blue and green laser and light-emitting diode design.
Article
Physics, Condensed Matter
I Gorczyca, G. Staszczak, G. Targowski, E. Grzanka, J. Smalc-Koziorowska, K. Skrobas, T. Suski
Summary: The band structure and photoluminescence characteristics of InGaN-based double barrier superlattices were investigated. The results showed that the double barrier superlattices can significantly increase the tunability of the band gap within a specific range. The hybridization of wave functions and the built-in electric field are crucial for band gap engineering in the InGaN-related spectral range.
MICRO AND NANOSTRUCTURES
(2022)
