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2. Characterization of band offsets in Al$_x$In$_{1-x}$As$_y$Sb$_{1-y}$ alloys with varying Al composition

Author

Zheng, Jiyuan, Jones, Andrew H., Tan, Yaohua, Rockwell, Ann K., March, Stephen, Ahmed, Sheikh Z., Dukes, Catherine A., Ghosh, Avik W., Bank, Seth R., and Campbell, Joe C.

Subjects
Condensed Matter - Materials Science
Abstract

The unprecedented wide bandgap tunability (~1 eV) of Al$_x$In$_{1-x}$As$_y$Sb$_{1-y}$ latticed-matched to GaSb enables the fabrication of photodetectors over a wide range from near-infrared to mid-infrared. In this paper, the valence band-offsets in AlxIn1-xAsySb1-y with different Al compositions are analyzed by tight-binding calculations and X-ray photoelectron spectroscopy (XPS) measurements. The observed weak variation in valence band offsets is consistent with the lack of any minigaps in the valence band, compared to the conduction band.

Published
2021

3. Full band Monte Carlo simulation of AlInAsSb digital alloys

Author

Zheng, Jiyuan, Ahmed, Sheikh Z., Yuan, Yuan, Jones, Andrew, Tan, Yaohua, Rockwell, Ann K., March, Stephen D., Bank, Seth R., Ghosh, Avik W., and Campbell, Joe C.

Subjects
Condensed Matter - Materials Science
Abstract

Avalanche photodiodes fabricated from AlInAsSb grown as a digital alloy exhibit low excess noise. In this paper, we investigate the band structure-related mechanisms that influence impact ionization. Band-structures calculated using an empirical tight-binding method and Monte Carlo simulations reveal that the mini-gaps in the conduction band do not inhibit electron impact ionization. Good agreement between the full band Monte Carlo simulations and measured noise characteristics is demonstrated.

Published
2021

6. ERIS: revitalising an adaptive optics instrument for the VLT

Author

Davies, Richard, Esposito, Simone, Schmid, Hans Martin, Taylor, William, Agapito, Guido, Berbel, Alexander Agudo, Baruffolo, Andrea, Biliotti, Valdemaro, Biller, Beth, Black, Martin, Boehle, Anna, Briguglio, Runa, Buron, Alexander, Carbonaro, Luca, Cortes, Angela, Cresci, Giovanni, Deysenroth, Matthias, Di Cianno, Amico, Di Rico, Gianluca, Doelman, David, Dolci, Mauro, Dorn, Reinhold, Eisenhauer, Frank, Fantinel, Daniela, Ferruzzi, Debora, Feuchtgruber, Helmut, Schreiber, Natascha Förster, Gao, Xiaofeng, Gemperlein, Hans, Genzel, Reinhard, George, Elizabeth, Gillessen, Stefan, Giordano, Christophe, Glauser, Adrian, Glindemann, Andreas, Grani, Paolo, Hartl, Michael, Heijmans, Jeroen, Henry, David, Huber, Heinrich, Kasper, Markus, Keller, Christoph, Kenworthy, Matthew, Kuehn, Jonas, Kuntschner, Harald, Lightfood, John, Lunney, David, MacIntosh, Mike, Mannucci, Filippo, March, Stephen, Neeser, Mark, Patapis, Polychronis, Pearson, David, Plattner, Markus, Puglisi, Alfio, Quanz, Sascha, Rau, Christian, Riccardi, Armando, Salasnich, Bernardo, Schubert, Josef, Snik, Frans, Sturm, Eckhard, Valentini, Angelo, Waring, Christopher, Wiezorrek, Erich, and Xompero, Marco

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

ERIS is an instrument that will both extend and enhance the fundamental diffraction limited imaging and spectroscopy capability for the VLT. It will replace two instruments that are now being maintained beyond their operational lifetimes, combine their functionality on a single focus, provide a new wavefront sensing module that makes use of the facility Adaptive Optics System, and considerably improve their performance. The instrument will be competitive with respect to JWST in several regimes, and has outstanding potential for studies of the Galactic Center, exoplanets, and high redshift galaxies. ERIS had its final design review in 2017, and is expected to be on sky in 2020. This contribution describes the instrument concept, outlines its expected performance, and highlights where it will most excel., Comment: 12 pages, Proc SPIE 10702 "Ground-Based and Airborne Instrumentation for Astronomy VII"

Published
2018

10. Structural and ferromagnetic properties of an orthorhombic phase of MnBi stabilized with Rh additions

Author

Taufour, Valentin, Thimmaiah, Srinivasa, March, Stephen, Saunders, Scott, Sun, Kewei, Lamichhane, Tej Nath, Kramer, Matthew J., Budko, Sergey L., and Canfield, Paul C.

Subjects
Condensed Matter - Materials Science
Abstract

The article addresses the possibility of alloy elements in MnBi which may modify the thermodynamic stability of the NiAs-type structure without significantly degrading the magnetic properties. The addition of small amounts of Rh and Mn provides an improvement in the thermal stability with some degradation of the magnetic properties. The small amounts of Rh and Mn additions in MnBi stabilize an orthorhombic phase whose structural and magnetic properties are closely related to the ones of the previously reported high-temperature phase of MnBi (HT~MnBi). To date, the properties of the HT~MnBi, which is stable between $613$ and $719$~K, have not been studied in detail because of its transformation to the stable low-temperature MnBi (LT~MnBi), making measurements near and below its Curie temperature difficult. The Rh-stabilized MnBi with chemical formula Mn$_{1.0625-x}$Rh$_{x}$Bi [$x=0.02(1)$] adopts a new superstructure of the NiAs/Ni$_2$In structure family. It is ferromagnetic below a Curie temperature of $416$~K. The critical exponents of the ferromagnetic transition are not of the mean-field type but are closer to those associated with the Ising model in three dimensions. The magnetic anisotropy is uniaxial; the anisotropy energy is rather large, and it does not increase when raising the temperature, contrary to what happens in LT~MnBi. The saturation magnetization is approximately $3$~$\mu_B$/f.u. at low temperatures. While this exact composition may not be application ready, it does show that alloying is a viable route to modifying the stability of this class of rare-earth-free magnet alloys., Comment: 9 pages, 10 figures

Published
2015
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15. The application of high temperature superconducting materials to power switches

Author

March, Stephen A. and Yang, Yifeng

Subjects
537.623, TK Electrical engineering. Electronics Nuclear engineering, QC Physics
Abstract

Superconducting switches may nd application in superconducting magnet systems that require energy extraction. Such superconducting switches could be bypass-switches that are operated in conjunction with a parallel resistor or dump-switches where all of the energy is dissipated in the switch itself. Bypass-switches are more suited to higher energy circuits as a portion of the energy can be dissipated in the external dump resistor. Dump-switches require less material and triggering energy as a lower switch resistance is needed to achieve the required total dump resistance. Both superconducting bypass-switches and superconducting dump-switches can be thermally activated. Switching times that are comparable to those obtained with mechanical bypass-switch systems can be achieved using a co-wound heater that is powered by a capacitor discharge. Switches that have fast thermal diffusion times through the insulation can be modelled as a lumped system whereas those with slow thermal diffusion times were modelled with the full heat diffusion equation. Superconducting switches can be formed of either high temperature superconductors (HTS) or low temperature superconductors (LTS). Switches based on HTS materials allow operation at higher temperatures where the cost of cooling is less. Extracting the magnet energy and depositing the heater energy at higher temperatures will also reduce the load on the overall cryogenic system during switching and energy extraction. For magnet circuits that are based on high temperature superconductors the switch must also be formed of HTS material. Due to the approximately T3 dependence of specific heat capacity, switches that operate at higher temperatures have slower heat diffusion times and require higher triggering energies than those operating at low temperature. HTS based dump-switches and HTS based bypass-switches were tested in liquid nitrogen to show that the required switching time could be achieved at these high temperatures. The design and optimisation of superconducting switches that were formed of various superconducting materials were performed for example magnet circuits to provide reference designs of switches. These example circuits were based on selected Large Hadron Collider 600 A circuits that had a stored energy of 5.5 kJ. Superconducting switches may also nd application in magnet circuits with higher transport currents and higher energies. The scaling and suitability of the reference designs to higher energy circuits was also described.

Published
2009

24. Low-noise AlxIn₁₋xAsySb₁₋y digital alloy staircase avalanche photodiodes grown by molecular beam epitaxy

Author

March, Stephen Daniel and 0000-0002-8938-050X

Subjects
Avalanche photodiode, Molecular beam epitaxy
Abstract

We present AlInAsSb digital alloy staircase avalanche photodiodes (APDs) grown on GaSb substrates with low-noise behavior for near- to mid-infrared optical sensing applications. Detectors that rely on electron ionization, such as traditional APDs or photomultiplier tubes, suffer from non-deterministic gain, which manifests itself in the form of noise. In this work, we leverage the widely tunable AlInAsSb band parameters afforded by the digital alloy growth technique to design multi-step staircase APDs that incorporate deterministic spatial localization of impact ionization events. Using these methods, we demonstrate the first implementation of staircase APDs with deterministic 2 [superscript N] gain, extremely low excess noise (F(M) ~ 1.1), and linear noise power scaling with gain, unlike the quadratic relationship observed in conventional APD noise. We further explore the staircase APD design with electrostatic and Monte Carlo simulation analyses to study low-noise APD carrier dynamics, namely: thermionic emission, tunneling, and impact ionization. Furthermore, we use the knowledge gained from those parameterization studies to produce 4- and 5-step staircase APDs. Future work will focus on the pursuing higher step counts to reap the benefits of the low-noise, deterministic gain characteristics of the staircase APD architecture. Additional work will focus on wavelength-flexible staircase APDs for low-noise mid-IR sensing applications

Published
2021
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30. Interactive youth science workshops benefit student participants and graduate student mentors

Author

Kompella, Pallavi, primary, Gracia, Brant, additional, LeBlanc, Lucy, additional, Engelman, Shelly, additional, Kulkarni, Chinmayee, additional, Desai, Niral, additional, June, Viviana, additional, March, Stephen, additional, Pattengale, Sarah, additional, Rodriguez-Rivera, Gabriel, additional, Ryu, Seung Woo, additional, Strohkendl, Isabel, additional, Mandke, Pooja, additional, and Clark, Greg, additional

Published
2020
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31. Full band Monte Carlo simulation of AlInAsSb digital alloys

Author

Zheng, Jiyuan, primary, Ahmed, Sheikh Z., additional, Yuan, Yuan, additional, Jones, Andrew, additional, Tan, Yaohua, additional, Rockwell, Ann K., additional, March, Stephen D., additional, Bank, Seth R., additional, Ghosh, Avik W., additional, and Campbell, Joe C., additional

Published
2020
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37. Composition-dependent structural transition in epitaxial Bi1−xSbx thin films on Si(111)

Author

Walker, Emily S., primary, Muschinske, Sarah, additional, Brennan, Christopher J., additional, Na, Seung Ryul, additional, Trivedi, Tanuj, additional, March, Stephen D., additional, Sun, Yukun, additional, Yang, Tianhao, additional, Yau, Alice, additional, Jung, Daehwan, additional, Briggs, Andrew F., additional, Krivoy, Erica M., additional, Lee, Minjoo L., additional, Liechti, Kenneth M., additional, Yu, Edward T., additional, Akinwande, Deji, additional, and Bank, Seth R., additional

Published
2019
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38. Photo-induced terahertz near-field dynamics of graphene/InAs heterostructures

Author

Yao, Ziheng, primary, Semenenko, Vyacheslav, additional, Zhang, Jiawei, additional, Mills, Scott, additional, Zhao, Xiaoguang, additional, Chen, Xinzhong, additional, Hu, Hai, additional, Mescall, Ryan, additional, Ciavatti, Thomas, additional, March, Stephen, additional, Bank, Seth R., additional, Tao, Tiger H., additional, Zhang, Xin, additional, Perebeinos, Vasili, additional, Dai, Qing, additional, Du, Xu, additional, and Liu, Mengkun, additional

Published
2019
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40. Digital Alloy Growth of Low-Noise Avalanche Photodiodes

Author

Bank, Seth R., primary, Campbell, Joe C., additional, Maddox, Scott J., additional, Rockwell, Ann Kathryn, additional, Woodson, Maddy E., additional, Ren, Min, additional, Jones, Andrew, additional, March, Stephen, additional, Zheng, Jiyuan, additional, and Yuan, Yuan, additional

Published
2018
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45. Development of cryogenic mechanisms for the VLT/ERIS instrument

Author

Glauser, Adrian M., primary, Bachmann, Walter, primary, March, Stephen, primary, Patapis, Polychronis, primary, MacIntosh, Michael, primary, Pearson, David, primary, Taylor, William D., primary, Quanz, Sascha P., primary, Schmid, Hans Martin, primary, Davies, Ric, primary, Feuchtgruber, Helmut, primary, Rau, Christian, primary, and Waring, Chris, primary

Published
2018
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48. ERIS, first generation becoming second generation, or re-vitalizing an AO instrument

Author

Cortes, Angela, primary, Davies, Richard, additional, Feuchtgruber, Helmut, additional, Sturm, Eckhard, additional, Eisenhauer, Frank, additional, Wiezzorek, Erich, additional, Schubert, Josef, additional, Rau, Christian, additional, Plattner, Markus, additional, Huber, Heinrich, additional, Hartl, Michael, additional, Gillessen, Stefan, additional, Förster-Schreiber, Natascha, additional, Buron, Alexander, additional, Di Rico, Gianluca, additional, Di Cianno, Amico, additional, Valentini, Angelo, additional, Dolci, Mauro, additional, Salasnich, Bernardo, additional, Fantinel, Daniela, additional, Baruffolo, Andrea, additional, Xompero, Marco, additional, Riccardi, Armando, additional, Puglisi, Alfio, additional, Mannucci, Filippo, additional, Giordano, Christophe, additional, Ferruzzi, Debora, additional, Esposito, Simone, additional, Cresci, Giovanni, additional, Carbonaro, Luca, additional, Briguglio, Runa, additional, Biliotti, Valdemaro, additional, Agapito, Guido, additional, Kenworthy, Matthew, additional, Keller, Christoph, additional, Snik, Frans, additional, Schmid, Hans Martin, additional, Quanz, Sascha, additional, March, Stephen, additional, Kuehn, Jonas, additional, Glauser, Adrian, additional, Kuntschner, Harald, additional, Kasper, Markus, additional, Glindemann, Andreas, additional, Dorn, Reinhold, additional, Jeroen, Heijmans, additional, Biller, Beth, additional, Waring, Christopher, additional, Taylor, William, additional, Pearson, David, additional, MacIntosh, Mike, additional, Lunney, David, additional, Lightfood, John, additional, Henry, David, additional, and Gao, Xiaofeng, additional

Published
2017
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