Article
Nanoscience & Nanotechnology
Patrick Vogt, Felix V. E. Hensling, Kathy Azizie, Celesta S. Chang, David Turner, Jisung Park, Jonathan P. McCandless, Hanjong Paik, Brandon J. Bocklund, Georg Hoffman, Oliver Bierwagen, Debdeep Jena, Huili G. Xing, Shin Mou, David A. Muller, Shun-Li Shang, Zi-Kui Liu, Darrell G. Schlom
Summary: Introduces a growth method called suboxide molecular-beam epitaxy (S-MBE) that significantly enhances the growth rates of Ga2O3 and related materials while maintaining excellent crystalline quality, applicable to a wide range of oxide materials.
Article
Engineering, Electrical & Electronic
Yue Kuang, Xuanhu Chen, Tongchuan Ma, Qianqian Du, Yanfang Zhang, Jinggang Hao, Fang-Fang Ren, Bin Liu, Shunming Zhu, Shulin Gu, Rong Zhang, Youdou Zheng, Jiandong Ye
Summary: This study successfully constructed the heterostructure of single crystalline metastable orthorhombic kappa-Ga2O3 epilayers and cubic In2O3 (111) using laser molecular beam epitaxy. Analysis of XPS and Hall results revealed the formation of a two-dimensional electron gas at the heterostructure interface with high carrier concentration and mobility.
ACS APPLIED ELECTRONIC MATERIALS
(2021)
Article
Physics, Applied
D. N. Lobanov, K. E. Kudryavtsev, M. Kalinnikov, L. Krasilnikova, P. A. Yunin, E. Skorokhodov, M. Shaleev, A. Novikov, B. A. Andreev, Z. F. Krasilnik
Summary: This study reports on stimulated emission (SE) in the near-infrared range from planar InGaN epitaxial layers grown on sapphire substrates. The research found that at temperatures around 190-210K, nonradiative recombination processes dominate the temperature quenching of stimulated emission. Different defect centers play a role in providing free electrons for both InN and InGaN layers, affecting the Shockley-Read-Hall (SRH) recombination rate at high temperatures.
APPLIED PHYSICS LETTERS
(2021)
Article
Physics, Applied
I. Ahmed, S. De Gendt, C. Merckling
Summary: The BaBiO3 perovskite oxide is an interesting material system that exhibits superconductivity when p-doped and predicted topological insulation when n-doped. High-quality single crystalline BaBiO3 films are grown on Si(001) substrates using molecular beam epitaxy, with the growth window established by systematically varying growth parameters.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Nanoscience & Nanotechnology
Kenny Huynh, Michael E. Liao, Akhil Mauze, Takeki Itoh, Xingxu Yan, James S. Speck, Xiaoqing Pan, Mark S. Goorsky
Summary: The orientational dependence of interfacial reaction between aluminum and different β-Ga2O3 substrates (010, (001), and ((2) over bar 01)) was investigated. It was found that the orientation of β-Ga2O3 substrates influences the formation of aluminum oxide layers and diffusional pathways.
Article
Chemistry, Multidisciplinary
Babak Nikoobakht, Aaron C. Johnston-Peck, David Laleyan, Ping Wang, Zetian Mi
Summary: A novel approach was presented for growth of surface-directed spinel ZnGa2O4 and beta-Ga2O3 nanofins coated with a non-polar GaN shell, utilizing a vacancy-assisted mechanism for exchange between Zn and Ga. The predictability over surface registries and tunable porosity of the core/shell fins is anticipated to be significant for various applications.
Article
Physics, Multidisciplinary
Zhen-Hua Li, Peng-Fei Shao, Gen-Jun Shi, Yao-Zheng Wu, Zheng-Peng Wang, Si-Qi Li, Dong-Qi Zhang, Tao Tao, Qing-Jun Xu, Zi-Li Xie, Jian-Dong Ye, Dun-Jun Chen, Bin Liu, Ke Wang, You-Dou Zheng, Rong Zhang
Summary: A systematic investigation on low growth rate PA-MBE grown GaN was conducted in a wide growth temperature range, identifying the optimal growth temperature window of 700-760 degrees C. The slightly Ga-rich region was preferred for high-quality GaN epitaxial growth. Mg and Si doped GaN resulted in both p- and n-type materials.
Article
Physics, Applied
Mengen Wang, Sai Mu, Chris G. Van de Walle
Summary: Studies suggest that silicon and tin can replace gallium sites in Ga2O3 and prefer different structural sites. Under surface reconstructions, silicon and tin may also occupy thermodynamically less preferred sites.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Tuo Sheng, Xing-Zhao Liu, Ling-Xuan Qian, Bo Xu, Yi-Yu Zhang
Summary: Metal-semiconductor-metal solar-blind ultraviolet photoconductors based on beta-Ga2O3 thin films were fabricated and the effects of annealing on their characteristics and photoconductivity were studied. Higher annealing temperature resulted in lower crystalline quality and device photoresponsivity. The vacuum-annealed sample showed the highest photoresponsivity and the oxygen-annealed sample effectively suppressed persistent photoconductivity.
Article
Nanoscience & Nanotechnology
Tobias Hadamek, Agham B. Posadas, Fatima Al-Quaiti, David J. Smith, Martha R. McCartney, Alexander A. Demkov
Summary: In this study, beta-Ga2O3 thin films were grown on a silicon surface using plasma-assisted molecular beam epitaxy at different temperatures. The structural characteristics of the films were analyzed through various testing methods, and atomistic models of gallia-alumina interfaces were proposed based on the results.
Article
Chemistry, Multidisciplinary
Karol Olszewski, Marta Sobanska, Vladimir G. Dubrovskii, Egor D. Leshchenko, Aleksandra Wierzbicka, Zbigniew R. Zytkiewicz
Summary: This study focused on the growth of GaN nanowires on Si(111) substrates using plasma-assisted molecular beam epitaxy, specifically investigating the orientation and growth rate of the nanowires. The researchers found that vertically aligned nanowires grew faster and produced more regular ensembles compared to inclined nanowires. These densely packed ensembles of vertically aligned GaN nanowires on ZrN/Si(111) surfaces are highly relevant for device applications.
Article
Crystallography
Ying-Chieh Wang, Ikai Lo, Yu-Chung Lin, Cheng-Da Tsai, Ting-Chang Chang
Summary: Mg-doped GaN was grown using plasma-assisted molecular beam epitaxy (PAMBE) on a Fe-doped GaN template substrate with a shutter-controlled process. The relationship between the N/Ga flux ratio and the transition from n-type to p-type conductivity of Mg-doped GaN was studied. The presence of Mg flux improved crystal quality and carrier mobility by preventing the formation of structural defects in GaN epi-layers.
Article
Engineering, Electrical & Electronic
Nikita Yakovlev, Aleksei Almaev, Pavel Butenko, David Tetelbaum, Alexey Mikhaylov, Alena Nikolskaya, Aleksei Pechnikov, Sergey Stepanov, Mikhail Boiko, Andrei Chikiryaka, Vladimir Nikolaev
Summary: The effect of Si+ ion implantation on the gas-sensing properties of (0001) alpha-Ga2O3 films grown by HVPE has been investigated. The results show that irradiation with a dose of 8 x 10(12) - 8 x 10(15) cm(-2) at an energy of 100 keV followed by postimplantation annealing significantly enhances the response of alpha-Ga2O3 films to 3 vol% of H-2 at 400 degrees C, reduces the response time by a factor of 6, and extends the operating temperature range to 30 degrees C. Additionally, alpha-Ga2O3 layers irradiated with a Si+ dose of 8 x 10(13) - 8 x 10(15) cm(-2) exhibit high sensitivity to CO and NH3 gases. A mechanism for the effect of Si+ ion irradiation on the gas-sensing properties of alpha-Ga2O3 structures is proposed.
IEEE SENSORS JOURNAL
(2023)
Article
Materials Science, Coatings & Films
Fedor Hrubisak, Kristina Husekova, Xiang Zheng, Alica Rosova, Edmund Dobrocka, Milan Tapajna, Matej Micusik, Peter Nadazdy, Fridrich Egyenes, Javad Keshtkar, Eva Kovacova, James W. Pomeroy, Martin Kuball, Filip Gucmann
Summary: In this study, monoclinic ss-Ga2O3 and orthorhombic kappa-Ga2O3 thin films were grown on highly thermally conductive 4H-SiC substrates using liquid-injection metal-organic chemical vapor deposition. Both gallium precursors produced the ss phase, but only the latter led to growth of kappa-Ga2O3. The best growth conditions for ss-Ga2O3 were a temperature of 700 degrees C and O-2 flows in the range of 600-800 SCCM. For kappa-Ga2O3, a narrow growth window was observed, with the best results at a temperature of 600 degrees C and an O-2 flow of 800 SCCM. The results suggest the potential of integrating Ga2O3 and SiC for improved thermal management and reliability of future high power Ga2O3-based devices.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Crystallography
Ana Bengoechea-Encabo, Steven Albert, Michael Niehle, Achim Trampert, Enrique Calleja
Summary: Two different arrays of GaN nanocolumns with different average diameters were selectively grown on GaN-buffered Si(0 0 1) substrates. The footprint of the nanocolumns plays an important role in the crystalline quality, despite the low quality of the GaN buffer layer. These results are significant for the integration of GaN-based nano-devices with conventional Si(0 0 1) electronics platform.
JOURNAL OF CRYSTAL GROWTH
(2023)
Correction
Nanoscience & Nanotechnology
Patrick Vogt, Felix V. E. Hensling, Kathy Azizie, Celesta S. Chang, David Turner, Jisung Park, Jonathan P. McCandless, Hanjong Paik, Brandon J. Bocklund, Georg Hoffmann, Oliver Bierwagen, Debdeep Jena, Huili G. Xing, Shin Mou, David A. Muller, Shun-Li Shang, Zi-Kui Liu, Darrell G. Schlom
Article
Physics, Applied
Johannes Feldl, Martin Feneberg, Alexandra Papadogianni, Jonas Laehnemann, Takahiro Nagata, Oliver Bierwagen, Ruediger Goldhahn, Manfred Ramsteiner
Summary: The influence of Ga incorporation into cubic In2O3 on the electronic and vibrational properties is discussed for (In1-x,Ga-x)(2)O-3 alloy films. The absorption onset and fundamental bandgap exhibit a blueshift with increasing Ga content, as determined by spectroscopic ellipsometry and hard x-ray photoelectron spectroscopy. The dependence of the absorption onset and effective electron mass on electron concentration is derived from the infrared dielectric functions, while the influence of alloying on phonon modes is analyzed based on Raman spectroscopic measurements.
APPLIED PHYSICS LETTERS
(2021)
Article
Physics, Applied
Alexandra Papadogianni, Takahiro Nagata, Oliver Bierwagen
Summary: The alloying of In2O3 and Ga2O3 can modulate the properties of the parent compounds, such as the character of oxygen vacancies and the presence of a surface electron accumulation layer. The addition of Ga increases the electron density due to native defects, possibly caused by Ga-related unit-cell distortions. X-ray photoelectron spectroscopy measurements confirm the existence of a surface electron accumulation layer in all alloy films, and Hall and Seebeck measurements show negligible contribution of the surface electron accumulation layer to electron transport.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Nanoscience & Nanotechnology
Andrew J. Green, James Speck, Grace Xing, Peter Moens, Fredrik Allerstam, Krister Gumaelius, Thomas Neyer, Andrea Arias-Purdue, Vivek Mehrotra, Akito Kuramata, Kohei Sasaki, Shinya Watanabe, Kimiyoshi Koshi, John Blevins, Oliver Bierwagen, Sriram Krishnamoorthy, Kevin Leedy, Aaron R. Arehart, Adam T. Neal, Shin Mou, Steven A. Ringel, Avinash Kumar, Ankit Sharma, Krishnendu Ghosh, Uttam Singisetti, Wenshen Li, Kelson Chabak, Kyle Liddy, Ahmad Islam, Siddharth Rajan, Samuel Graham, Sukwon Choi, Zhe Cheng, Masataka Higashiwaki
Summary: Gallium Oxide has become a leading ultra-wide band gap semiconductor technology due to its favorable material properties. This roadmap presents the current state-of-the-art and future challenges in the field, aiming to enhance device performance and design efficient microelectronic systems.
Article
Physics, Applied
Kornelius Tetzner, Kingsley Egbo, Michael Klupsch, Ralph-Stephan Unger, Andreas Popp, Ta-Shun Chou, Saud Bin Anooz, Zbigniew Galazka, Achim Trampert, Oliver Bierwagen, Joachim Wuerfl
Summary: In this work, SnO/beta-Ga2O3 heterojunction vertical diodes and lateral field-effect transistors for power electronic applications were realized. The deposited films of p-type SnO on n-type (100) beta-Ga2O3 showed excellent electrical characteristics. The heterojunction diodes and field-effect transistors exhibited stable performance and demonstrated state-of-the-art electrical properties.
APPLIED PHYSICS LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Alexandra Papadogianni, Charlotte Wouters, Robert Schewski, Johannes Feldl, Jonas Lahnemann, Takahiro Nagata, Elias Kluth, Martin Feneberg, Rudiger Goldhahn, Manfred Ramsteiner, Martin Albrecht, Oliver Bierwagen
Summary: In this study, single-crystalline bixbyite (In1-xGax)(2)O-3 films were grown on (111)-oriented yttria-stabilized zirconia substrates using plasma-assisted molecular beam epitaxy. The addition of a pure In2O3 buffer layer between the substrate and (In1-xGax)(2)O-3 alloy improved the film surface smoothness and crystallinity. The distribution of Ga cations in the films was found to be non-uniform, with high Ga density inclusions observed at higher Ga content. The cubic bixbyite phase was preserved in both the matrix and the inclusions.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Laura E. Ratcliff, Takayoshi Oshima, Felix Nippert, Benjamin M. Janzen, Elias Kluth, Rudiger Goldhahn, Martin Feneberg, Piero Mazzolini, Oliver Bierwagen, Charlotte Wouters, Musbah Nofal, Martin Albrecht, Jack E. N. Swallow, Leanne A. H. Jones, Pardeep K. Thakur, Tien-Lin Lee, Curran Kalha, Christoph Schlueter, Tim D. Veal, Joel B. Varley, Markus R. Wagner, Anna Regoutz
Summary: Ga2O3 and its polymorphs have great potential for electronic structure engineering. In this study, a robust atomistic model of gamma-Ga2O3 is developed using density functional theory and machine-learning approach, which is validated by experimental results. This work is of significant importance for understanding the electronic structure of complex, disordered oxides.
ADVANCED MATERIALS
(2022)
Article
Materials Science, Coatings & Films
A. Parisini, P. Mazzolini, O. Bierwagen, C. Borelli, K. Egbo, A. Sacchi, M. Bosi, L. Seravalli, A. Tahraoui, R. Fornari
Summary: SnO/ ε-Ga2O3 vertical p-n diodes with planar geometry have been fabricated and investigated. The in-plane conduction through the Si-doped ε-Ga2O3 layer significantly affects the performance of the diodes, showing typical features of variable range hopping transport.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2022)
Article
Chemistry, Multidisciplinary
Daniel Pfuetzenreuter, Seonghyeon Kim, Hyeongmin Cho, Oliver Bierwagen, Martina Zupancic, Martin Albrecht, Kookrin Char, Jutta Schwarzkopf
Summary: This article reports the properties of conductance at the LaInO3/BaSnO3 heterointerface. It is found that a 2D electron gas (2DEG) is formed within the BaSnO3 layer, exhibiting a semiconductor behavior. Additionally, the mobility increases as the temperature decreases.
ADVANCED MATERIALS INTERFACES
(2022)
Article
Chemistry, Multidisciplinary
Piero Mazzolini, Zsolt Fogarassy, Antonella Parisini, Francesco Mezzadri, David Diercks, Matteo Bosi, Luca Seravalli, Anna Sacchi, Giulia Spaggiari, Danilo Bersani, Oliver Bierwagen, Benjamin Moritz Janzen, Marcella Naomi Marggraf, Markus R. Wagner, Ildiko Cora, Bela Pecz, Abbes Tahraoui, Alessio Bosio, Carmine Borelli, Stefano Leone, Roberto Fornari
Summary: Unintentionally doped kappa-Ga2O3 epitaxial films on sapphire substrates exhibit columnar rotational domains that inhibit in-plane electronic conduction. The introduction of silane doping increases the domain size and mobility, improving in-plane conduction. Non-destructive techniques based on X-ray diffraction and Raman spectroscopy can be used to compare domain dimensions.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Physics, Applied
Kingsley Egbo, Esperanza Luna, Jonas Laehnemann, Georg Hoffmann, Achim Trampert, Jona Gruembel, Elias Kluth, Martin Feneberg, Ruediger Goldhahn, Oliver Bierwagen
Summary: By combining SnO2 and Sn, we successfully grew phase-pure single-crystalline metastable SnO (001) thin films on Y-stabilized ZrO2 (001) substrates using suboxide molecular beam epitaxy (S-MBE) at a growth rate of about 1.0 nm/min without additional oxygen. These films exhibit epitaxial growth over a wide temperature range of 150 to 450°C. The obtained p-type SnO films at low substrate temperatures show promise for back-end-of-line (BEOL) compatible applications and integration with n-type oxides in pn heterojunctions and field-effect transistors.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Kingsley Egbo, Jonas Laehnemann, Andreas Falkenstein, Joel Varley, Oliver Bierwagen
Summary: (La and Ga)-doped tin monoxide thin films were grown with dopant concentrations ranging from approximate to 5 x 10(18) to 2 x 10(21) cm(-3). Ga acted as an acceptor and La as a compensating donor in the doped samples. The results show the possibilities of controlling the hole concentration in p-type SnO, which can be useful for a range of optoelectronic and gas-sensing applications.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Condensed Matter
Anna Reis, Michael Hanke, Oliver Bierwagen, Achim Trampert, Piero Mazzolini, Edmund Welter
Summary: The local ordering in amorphous Ga2O3 and (InxGa1-x)(2)O-3 thin films on Si(111) and its change on crystallization upon annealing were investigated. The bonding character of the Ga cations was studied using synchrotron-based extended X-ray absorption fine structure data and a numerical implementation of the scattering process. The results showed the preferential formation of GaO4 tetrahedrons in the amorphous films, while annealing led to the formation of monoclinic beta-Ga2O3 crystallites with both tetra- and octahedral coordination for the amorphous Ga2O3 film.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Rongbin Wang, Thorsten Schultz, Alexandra Papadogianni, Elena Longhi, Christos Gatsios, Fengshuo Zu, Tianshu Zhai, Stephen Barlow, Seth R. Marder, Oliver Bierwagen, Patrick Amsalem, Norbert Koch
Summary: In2O3, a transparent transition metal oxide, can have an enhanced or depleted surface electron accumulation layer (SEAL) depending on the density of oxygen vacancies at the surface. By adsorbing molecular electron donors or acceptors, the SEAL of In2O3 can be tuned. This work demonstrates that adsorption of [RuCp*mes](2) restores the SEAL, while adsorption of F(6)TCNNQ depletes the SEAL and generates upward band bending at the In2O3 surface.
Article
Materials Science, Multidisciplinary
Benjamin M. Janzen, Piero Mazzolini, Roland Gillen, Vivien F. S. Peltason, Linus P. Grote, Janina Maultzsch, Roberto Fornari, Oliver Bierwagen, Markus R. Wagner
Summary: Gallium oxide (Ga2O3) is a wide bandgap material with potential applications in power electronics and photodetectors. The orthorhombic kappa phase is of particular interest for its ferroelectric behavior and potential for high-quality electron gases. Investigation into the phonon modes of the material provides insights into its crystal structure and vibrational properties.
JOURNAL OF MATERIALS CHEMISTRY C
(2021)