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Steven Ringel

  • Executive Director - IMR, OR - Inst for Material Res
  • Professor, Neal A Smith Chair, Electrical & Computer Engr.
  • Professor, Materials Science Engineering
  • Professor, Physics
  • Room #375
    2024 Neil Ave
    Columbus, OH 43210
  • 614-292-6904

About

Education

Ph.D. 1991, Georgia Institute of Technology

Areas of interest

Electronic materials; optoelectronics, photovoltaics, molecular beam epitaxy, compound semiconductors, nanostructures, defect and interfaces, optoelectronic integrated circuits.

Office

375 Caldwell Laboratory

Personal website

http://emdl.ece.ohio-state.edu/index.html

Honors

  • 2005

    AAAS Fellow.

  • 1999

    Stanley E. Harrison Faculty Award for Excellence in Engineering. .

  • 1994

    National Young Investigator Award.

Chapters

2006

  • Wilt, D. M.; Ringel, S. A.; Fitzgerald, E. A.; Jenkins, P. P.; Walters, R.. 2006. In Conference Record of the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion (IEEE Cat. No. 06CH37747), IEEE.
  • Lee, K.; VanMil, B.; Luo, M.; Myers, T. H.; Armstrong, A.; Ringel, S. A.; Rummukainen, M.; Saarinen, K.. 2006. In GaN, AlN, InN and Related Materials. Symposium (Materials Research Society Symposium Proceedings Vol.892), Materials Research Society.
  • Ringel, S. A.; Kwon, O.; Lueck, M.; Boeckl, J.; Fitzgerald, E. A.. 2006. In 2006 International SiGe Technology and Device Meeting (IEEE Cat. No. 06EX1419), IEEE.
  • Liu, D.; Hudait, M.; Lin, Y.; Kim, H.; Ringel, S. A.; Lu, W.. 2006. In 2005 Asia-Pacific Microwave Conference, IEEE.

2005

  • Dongmin Liu; Hudait, M.; Yong Lin; Hyeongnam Kim; Ringel, S. A.; Wu Lu. 2005. In 2005 International Semiconductor Device Research Symposium (IEEE Cat. No.05EX1272C), IEEE.
  • Wilt, D. M.; Pal, A. M. T.; Prokop, N. F.; Ringel, S. A.; Andre, Cl.; Smith, M. A.; Scheiman, D. A.; Jenkins, P. P.; Maurer, W. F.; McElroy, B.; Fitzgerald, E. A.. 2005. In Conference Record of the Thirty-First IEEE Photovoltaic Specialist Conference (IEEE Cat. No. 05CH37608), IEEE.
  • Ringel, S. A.; Andre, C. L.; Lueck, M.; Isaacson, D.; Pitera, A. J.; Fitzgerald, E. A.; Wilt, D. M.. 2005. In Materials for Photovoltaics. Symposium (Materials Research Society Symposium Proceedings Vol.836), Materials Research Society.
  • Lueck, M.; Gonzalez, M.; Ojin Kwon; Andre, C.; Ringel, S. A.. 2005. In Conference Record of the Thirty-First IEEE Photovoltaic Specialist Conference (IEEE Cat. No. 05CH37608), IEEE.
  • Ringel, S. A.; Andre, C. L.; Fitzgerald, E. A.; Pitera, A. J.; Wilt, D. M.. 2005. In Conference Record of the Thirty-First IEEE Photovoltaic Specialist Conference (IEEE Cat. No. 05CH37608), IEEE.
  • Armstrong, A.; Green, D.; Arehart, A. R.; Mishra, U. K.; Speck, J. S.; Ringel, S. A.. 2005. In GaN, AlN, InN and Their Alloys. Symposium (Materials Research Society Symposium Proceedings Vol.831), Materials Research Society.

2004

  • Armstrong, A.; Arehart, A. R.; Ringel, S. A.; Moran, B.; Denbaars, S. P.; Mishra, U. K.; Speck, J. S.. 2004. In GaN and Related Alloys - 2003 Symposium (Mater. Res. Soc. Symposium Proceedings Vol.798), Mater. Res. Soc.
  • Arehart, A. R.; Poblenz, C.; Heying, B.; Speck, J. S.; Mishra, U. K.; DenBaars, S. P.; Ringel, S. A.. 2004. In GaN and Related Alloys - 2003 Symposium (Mater. Res. Soc. Symposium Proceedings Vol.798), Mater. Res. Soc.
  • Armstrong, A.; Arehart, A. R.; Moran, B.; DenBaars, S. P.; Mishra, U. K.; Speck, J. S.; Ringel, S. A.. 2004. In 2003 International Symposium on Compound Semiconductors: Post-Conference Proceedings (IEEE Cat. No.03TH8767), IEEE.

2003

  • Ringel, S. A.; Andre, C. L.; Hudait, M. K.; Wilt, D. M.; Clark, E. B.; Pitera, A. J.; Lee, M. L.; Fitzgerald, E. A.; Carroll, M.; Erdtmann, M.; Carlin, J. A.; Keyes, B. M.. 2003. In Proceedings of 3rd World Conference on Photovoltaic Energy Conversion (IEEE Cat. No.03CH37497), Arisumi Printing Inc.
  • Fitzgerald, E. A.; Groenart, M. E.; Pitera, A.; Lee, M. L.; Yang, V.; Carlin, J. A.; Leitz, C. W.; Andre, C. L.; Ringel, S. A.. 2003. In Proceedings of 3rd World Conference on Photovoltaic Energy Conversion (IEEE Cat. No.03CH37497), Arisumi Printing Inc.
  • Ringel, S. A.; Armstrong, A.; Arehart, A.; Moran, B.; Mishra, U. K.; Speck, J. S.. 2003. In 2003 International Symposium on Compound Semiconductors (Cat. No.03TH8675), IEEE.

2002

  • Hudait, M. K.; Lin, Y.; Andre, C. L.; Sinha, P. M.; Tivarus, C. A.; Pelz, J. P.; Wilt, D. M.; Ringel, S. A.. 2002. In Materials and Devices for Optoelectronics and Microphotonics. Symposia (Materials Research Society Symposium Proceedings Vol.722), Mater. Res. Soc.
  • Andre, C. L.; Khan, A.; Gonzalez, M.; Hudait, M. K.; Fitzgerald, E. A.; Carlin, J. A.; Currie, M. T.; Leitz, C. W.; Langdo, T. A.; Clark, E. B.; Wilt, D. M.; Ringel, S. A.. 2002. In Conference Record of the Twenty-Ninth IEEE Photovoltaic Specialists Conference 2002 (Cat. No.02CH37361), IEEE.

2000

  • Hierro, A.; Kwon, D.; Ringel, S. A.; Hansen, M.; Mishra, U. K.; DenBaars, S. P.; Speck, J. S.. 2000. In GaN and Related Alloys - 1999. Symposium (Materials Research Society Symposium Proceedings Vol.595), Mater. Res. Soc.
  • Carlin, J. A.; Hudait, M. K.; Ringel, S. A.; Wilt, D. M.; Clark, E. B.; Leitz, C. W.; Currie, M.; Langdo, T.; Fitzgerald, E. A.. 2000. In Conference Record of the Twenty-Eighth IEEE Photovoltaic Specialists Conference - 2000 (Cat. No.00CH37036), IEEE.
  • Hierro, A.; Boeckl, J. J.; Ringel, S. A.; Hansen, M.; Mishra, U. K.; Debaars, S. P.; Speck, J. S.; Look, D. C.. 2000. In Proceedings of International Workshop on Nitride Semiconductors, Inst. Pure & Appl. Phys.

1999

  • Daewon Kwon; Kaplar, R. J.; Beockl, J. J.; Ringel, S. A.; Allerman, A. A.; Kurtz, S. R.; Jones, E. D.. 1999. In III-V and IV-IV Materials and Processing Challenges for Highly Integrated Microelectronics and Optoelectronics. Symposium, Materials Res. Soc.
  • Ringel, S. A.; Carlin, J. A.; Sieg, R. M.; Boeckl, J. J.; Fitzgerald, E. A.. 1999. In Lattice Mismatched Thin Films. Proceedings of the First International Workshop, TMS - Miner. Metals & Mater. Soc.
  • Hierro, A.; Kwon, D.; Ringel, S. A.; Brillson, L. J.; Young, A. P.; Franciosi, A.. 1999. In III-V and IV-IV Materials and Processing Challenges for Highly Integrated Microelectronics and Optoelectronics. Symposium, Materials Res. Soc.

1998

  • Hoffman, R. W. , Jr.; Fatemi, N. S.; Weizer, V. G.; Jenkins, P.; Stan, M. A.; Ringel, S. A.; Sieg, R. M.; Scheiman, D. A.; Wilt, D. M.; Brinker, D. J.. 1998. In Thin-Film Structures for Photovoltaics. Symposium, Materials Research Society.

1997

  • Ringel, S. A.; Grillot, P. N.. 1997. In Defects in Electronic Materials II. Symposium, Mater. Res. Soc.
  • Ringel, S. A.; Sieg, R. M.; Ting, S. M.; Fitzgerald, E. A.. 1997. In Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997 (Cat. No.97CB36026), IEEE.
  • Chatterjee, B.; Ringel, S. A.; Hoffman, R. W. , Jr.. 1997. In Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997 (Cat. No.97CB36026), IEEE.
  • Hoffman, R. W. , Jr.; Fatemi, N. S.; Jenkins, P. P.; Weizer, V. G.; Stan, M. A.; Ringel, S. A.; Scheiman, D. A.; Wilt, D. M.; Brinker, D. J.; Walters, R. J.; Messenger, S. R.. 1997. In Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997 (Cat. No.97CB36026), IEEE.

1996

  • Chatterjee, B.; Ringel, S. A.; Hoffman, R. , Jr.. 1996. In Conference Record of the Twenty Fifth IEEE Photovoltaic Specialists Conference - 1996 (Cat. No.96CH35897), IEEE.
  • Hoffman, R. W. , Jr.; Fatemi, N. S.; Jenkins, P. P.; Scheiman, D. A.; Ringel, S. A.; Davis, W.; Weizer, V. G.; Wilt, D. M.; Brinker, D. J.. 1996. In Conference Record of the Twenty Fifth IEEE Photovoltaic Specialists Conference - 1996 (Cat. No.96CH35897), IEEE.

1994

  • Grillot, P. N.; Ringel, S. A.; Watson, G. P.; Fitzgerald, E. A.; Xie, Y. H.. 1994. In Physics and Applications of Defects in Advanced Semiconductors. Symposium, Mater. Res. Soc.
  • Chatterjee, B.; Ringel, S. A.; Sieg, R.; Weinberg, I.; Hoffman, R.. 1994. In Physics and Applications of Defects in Advanced Semiconductors. Symposium, Mater. Res. Soc.
  • Ringel, S. A.; Chatterjee, B.; Sieg, R. M.; Schnetzer, E. V.; Hoffman, R.. 1994. In 1994 IEEE First World Conference on Photovoltaic Energy Conversion. Conference Record of the Twenty Fourth IEEE Photovoltaic Specialists Conference-1994 (Cat.No.94CH3365-4), IEEE.

1991

  • Rohatgi, A.; Ringel, S. A.; Sudharsanan, R.; Chou, H. C.. 1991. In Conference Record of the Twenty Second IEEE Photovoltaic Specialists Conference - 1991 (Cat. No.91CH2953-8), IEEE.

1988

  • Ringel, S. A.; Rohatgi, A.. 1988. In Conference Record of the Twentieth IEEE Photovoltaic Specialists Conference - 1988 (Cat. No.88CH2527-0), IEEE.
  • Rohatgi, A.; Sudharsanan, R.; Ringel, S. A.; Meyers, P. V.; Liu, C. H.. 1988. In Conference Record of the Twentieth IEEE Photovoltaic Specialists Conference - 1988 (Cat. No.88CH2527-0), IEEE.

Journal Articles

2007

  • Lin, Y.; Carlin, J. A.; Arehart, A. R.; Carlin, A. M.; Ringel, S. A., 2007, "High-mobility two-dimensional electron gas in InAlAs/InAs heterostructures grown on virtual InAs substrates by molecular-beam epitaxy." Applied Physics Letters 90, no. 1,

2006

  • Liu, D.; Hudait, M.; Lin, Y.; Kim, H.; Ringel, S. A.; Lu, W., 2006, "In0.53Ga0.47As/InAs0.3P0.7 composite channel high electron mobility transistors." Electronics Letters 42, no. 5,
  • Min Gao; Bradley, S. T.; Yu Cao; Jena, D.; Lin, Y.; Ringel, S. A.; Hwang, J.; Schaff, W. J.; Brillson, L. J., 2006, "Compositional modulation and optical emission in AlGaN epitaxial films." Journal of Applied Physics 100, no. 10,
  • Kwon, O.; Boeckl, J. J.; Lee, M. L.; Pitera, A. J.; Fitzgerald, E. A.; Ringel, S. A., 2006, "Monolithic integration of AlGaInP laser diodes on SiGe/Si substrates by molecular beam epitaxy." Journal of Applied Physics 100, no. 1,
  • Gonzalez, M.; Andre, C. L.; Walters, R. J.; Messenger, S. R.; Warner, J. H.; Lorentzen, J. R.; Pitera, A. J.; Fitzgerald, E. A.; Ringel, S. A., 2006, "Deep level defects in proton radiated GaAs grown on metamorphic SiGe/Si substrates." Journal of Applied Physics 100, no. 3,
  • Hudait, M. K.; Lin, Y.; Sinha, P. M.; Lindemuth, J. R.; Ringel, S. A., 2006, "Carrier compensation and scattering mechanisms in Si-doped InAsyP1-y layers grown on InP substrates using intermediate InAsyP1-y step-graded buffers." Journal of Applied Physics 100, no. 6,
  • Lueck, M. R.; Andre, C. L.; Pitera, A. J.; Lee, M. L.; Fitzgerald, E. A.; Ringel, S. A., 2006, "Dual junction GaInP/GaAs solar cells grown on metamorphic SiGe/Si substrates with high open circuit voltage." IEEE Electron Device Letters 27, no. 3,
  • Armstrong, A.; Chakraborty, A.; Speck, J. S.; DenBaars, S. P.; Mishra, U. K.; Ringel, S. A., 2006, "Quantitative observation and discrimination of AlGaN- and GaN-related deep levels in AlGaN/GaN heterostructures using capacitance deep level optical spectroscopy." Applied Physics Letters 89, no. 26,

2005

  • Smith, P. E.; Goss, S. H.; Gao, M.; Hudait, M. K.; Lin, Y.; Ringel, S. A.; Brillson, L. J., 2005, "Atomic diffusion and band lineups at In0.53Ga0.47As-on-InP heterointerfaces." Journal of Vacuum Science & Technology B (Microelectronics and Nanometer Structures) 23, no. 4,
  • Tivarus, C.; Pelz, J. P.; Hudait, M. K.; Ringel, S. A., 2005, "Spatial resolution of ballistic electron emission microscopy measured on metal/quantum-well Schottky contacts." Applied Physics Letters 87, no. 18,
  • Tivarus, C.; Park, K. -B.; Hudait, M. K.; Ringel, S. A.; Pelz, J. P., 2005, "Nanoscale characterization of metal/semiconductor nanocontacts." AIP Conference Proceedings no. 788,
  • Tivarus, C.; Pelz, J. P.; Hudait, M. K.; Ringel, S. A., 2005, "Direct measurement of quantum confinement effects at metal to quantum-well nanocontacts." Physical Review Letters 94, no. 20,
  • Kwon, O.; Lin, Y.; Boeckl, J.; Ringel, S. A., 2005, "Growth and properties of digitally-alloyed AlGaInP by solid source molecular beam epitaxy." Journal of Electronic Materials 34, no. 10,
  • Lin, Y.; Hudait, M. K.; Johnston, S. W.; Ahrenkiel, R. K.; Ringel, S. A., 2005, "Photoconductivity decay in metamorphic InAsP/InGaAs double heterostructures grown on InAsyP1-y compositionally step-graded buffers." Applied Physics Letters 86, no. 7,
  • Kwon, O.; Boeckl, J.; Lee, M. L.; Pitera, A. J.; Fitzgerald, E. A.; Ringel, S. A., 2005, "Growth and properties of AlGaInP resonant cavity light emitting diodes on Ge/SiGe/Si substrates." Journal of Applied Physics 97, no. 3,
  • Gao, M.; Lin, Y.; Bradley, S. T.; Ringel, S. A.; Hwang, J.; Schaff, W. J.; Brillson, L. J., 2005, "Spontaneous compositional superlattice and band-gap reduction in Si-doped AlxGa1-xN epilayers." Applied Physics Letters 87, no. 19,
  • Andre, C. L.; Carlin, J. A.; Boeckl, J. J.; Wilt, D. M.; Smith, M. A.; Pitera, A. J.; Lee, M. L.; Fitzgerald, E. A.; Ringel, S. A., 2005, "Investigations of high-performance GaAs solar cells grown on Ge-Si1-xGex-Si substrates." IEEE Transactions on Electron Devices 52, no. 6,
  • Andre, C. L.; Wilt, D. M.; Pitera, A. J.; Lee, M. L.; Fitzgerald, E. A.; Ringel, S. A., 2005, "Impact of dislocation densities on n+/p and p+/n junction GaAs diodes and solar cells on SiGe virtual substrates." Journal of Applied Physics 98, no. 1,
  • Armstrong, A.; Arehart, A. R.; Ringel, S. A., 2005, "A method to determine deep level profiles in highly compensated, wide band gap semiconductors." Journal of Applied Physics 97, no. 8,
  • Armstrong, A.; Arehart, A. R.; Green, D.; Mishra, U. K.; Speck, J. S.; Ringel, S. A., 2005, "Impact of deep levels on the electrical conductivity and luminescence of gallium nitride codoped with carbon and silicon." Journal of Applied Physics 98, no. 5,
  • Armstrong, A.; Arehart, A.; Green, D.; Speck, J. S.; Mishra, U. K.; Ringel, S. A., 2005, "A novel method to investigate defect states in MBE grown highly resistive GaN doped with C and Si." Physica Status Solidi C no. 7,
  • Hudait, M. K.; Lin, Y.; Goss, S. H.; Smith, P.; Bradley, S.; Brillson, L. J.; Johnston, S. W.; Ahrenkiel, R. K.; Ringel, S. A., 2005, "Evidence of interface-induced persistent photoconductivity in InP/In0.53Ga0.47As/InP double heterostructures grown by molecular-beam epitaxy." Applied Physics Letters 87, no. 3,

2004

  • Smith, P. E.; Goss, S. H.; Bradley, S. T.; Hudait, M. K.; Lin, Y.; Ringel, S. A.; Brillson, L. J., 2004, "Atomic layer diffusion and electronic structure at In0.53Ga0.47As/InP interfaces." Journal of Vacuum Science & Technology B (Microelectronics and Nanometer Structures) 22, no. 2,
  • Armstrong, A.; Arehart, A. R.; Moran, B.; DenBaars, S. P.; Mishra, U. K.; Speck, J. S.; Ringel, S. A., 2004, "Impact of carbon on trap states in n-type GaN grown by metalorganic chemical vapor deposition." Applied Physics Letters 84, no. 3,
  • Andre, C. L.; Boeckl, J. J.; Wilt, D. M.; Pitera, A. J.; Lee, M. L.; Fitzgerald, E. A.; Keyes, B. M.; Ringel, S. A., 2004, "Impact of dislocations on minority carrier electron and hole lifetimes in GaAs grown on metamorphic SiGe substrates." Applied Physics Letters 84, no. 18,
  • Hudait, M. K.; Lin, Y.; Palmisiano, M. N.; Tivarus, C.; Pelz, J. P.; Ringel, S. A., 2004, "Comparison of mixed anion, InAsyP1-y and mixed cation, InxAl1-xAs metamorphic buffers grown by molecular beam epitaxy on (100) InP substrates." Journal of Applied Physics 95, no. 8,

2003

  • Hudait, M. K.; Lin, Y.; Palmisiano, M. N.; Ringel, S. A., 2003, "0.6-eV bandgap In0.69Ga0.31As thermophotovoltaic devices grown on InAsyP1-y step-graded buffers by molecular beam epitaxy." IEEE Electron Device Letters 24, no. 9,
  • Hudait, M. K.; Lin, Y.; Wilt, D. M.; Speck, J. S.; Tivarus, C. A.; Heller, E. R.; Pelz, J. P.; Ringel, S. A., 2003, "High-quality InAsyP1-y step-graded buffer by molecular-beam epitaxy." Applied Physics Letters 82, no. 19,
  • Kwon, O.; Jazwiecki, M. M.; Sacks, R. N.; Ringel, S. A., 2003, "High-performance, metamorphic InxGa1-xAs tunnel diodes grown by molecular beam epitaxy." IEEE Electron Device Letters 24, no. 10,

2002

  • Kaplar, R. J.; Ringel, S. A.; Kurtz, S. R.; Klem, J. F.; Allerman, A. A., 2002, "Deep-level defects in InGaAsN grown by molecular-beam epitaxy." Applied Physics Letters 80, no. 25,
  • Ringel, S. A.; Carlin, J. A.; Andre, C. L.; Hudait, M. K.; Gonzalez, M.; Wilt, D. M.; Clark, E. B.; Jenkins, P.; Scheiman, D.; Allerman, A.; Fitzgerald, E. A.; Leitz, C. W., 2002, "Single junction InGaP/GaAs solar cells grown on Si substrates with site buffer layers." Progress in Photovoltaics: Research and Applications 10, no. 6,
  • Hierro, A.; Arehart, A. R.; Heying, B.; Hansen, M.; Mishra, U. K.; DenBaars, S. P.; Speck, J. S.; Ringel, S. A., 2002, "Impact of Ga/N flux ratio on trap states in n-GaN grown by plasma-assisted molecular-beam epitaxy." Applied Physics Letters 80, no. 5,
  • Hudait, M. K.; Andre, C. L.; Kwon, O.; Palmisiano, M. N.; Ringel, S. A., 2002, "High-performance In0.53Ga0.47As thermophotovoltaic devices grown by solid source molecular beam epitaxy." IEEE Electron Device Letters 23, no. 12,

2001

  • Kaplar, R. J.; Arehart, A. R.; Ringel, S. A.; Allerman, A. A.; Sieg, R. M.; Kurtz, S. R., 2001, "Deep levels and their impact on generation current in Sn-doped InGaAsN." Journal of Applied Physics 90, no. 7,
  • Kaplar, R. J.; Kwon, D.; Ringel, S. A.; Allerman, A. A.; Kurtz, S. R.; Jones, E. D.; Sieg, R. M., 2001, "Deep levels in p- and n-type InGaAsN for high-efficiency multi-junction III-V solar cells." Solar Energy Materials and Solar Cells 69, no. 1,
  • Carlin, J. A.; Ringel, S. A.; Fitzgerald, A.; Bulsara, M., 2001, "High-lifetime GaAs on Si using GeSi buffers and its potential for space photovoltaics." Solar Energy Materials and Solar Cells 66, no. 1-4,
  • Hierro, A.; Hansen, M.; Boeckl, J. J.; Zhao, L.; Speck, J. S.; Mishra, U. K.; DenBaars, S. P.; Ringel, S. A., 2001, "Carrier trapping and recombination at point defects and dislocations in MOCVD n-GaN." Physica Status Solidi B 228, no. 3,

2000

  • Hierro, A.; Kwon, D.; Ringel, S. A.; Rubini, S.; Pelucchi, E.; Franciosi, A., 2000, "Photocapacitance study of bulk deep levels in ZnSe grown by molecular-beam epitaxy." Journal of Applied Physics 87, no. 2,
  • Hierro, A.; Ringel, S. A.; Hansen, M.; Speck, J. S.; Mishra, U. K.; DenBaars, S. P., 2000, "Hydrogen passivation of deep levels in n-GaN." Applied Physics Letters 77, no. 10,
  • Hierro, A.; Kwon, D.; Ringel, S. A.; Hansen, M.; Speck, J. S.; Mishra, U. K.; DenBarrs, S. P., 2000, "Optically and thermally detected deep levels in n-type Schottky and p+-n GaN diodes." Applied Physics Letters 76, no. 21,
  • Carlin, J. A.; Ringel, S. A.; Fitzgerald, E. A.; Bulsara, M.; Keyes, B. M., 2000, "Impact of GaAs buffer thickness on electronic quality of GaAs grown on graded Ge/GeSi/Si substrates." Applied Physics Letters 76, no. 14,
  • Carlin, J. A.; Ringel, S. A.; Fitzgerald, E. A.; Bulsara, M., 2000, "High quality GaAs growth by MBE on Si using GeSi buffers and prospects for space photovoltaics." Progress in Photovoltaics: Research and Applications 8, no. 3,

1999

  • Ringel, S. A.; Sacks, R. N.; Qin, L.; Clevenger, M. B.; Murray, C. S., 1999, "Growth and properties of InGaAs/FeAl/InAlAs/InP heterostructures for buried reflector/interconnect applications in InGaAs thermophotovoltaic devices." AIP Conference Proceedings no. 460,
  • Sacks, R. N.; Qin, A.; Jazwiecki, M.; Ringel, S. A.; Clevenger, M. B.; Wilt, D.; Goorsky, M. S., 1999, "Growth and characterization of epitaxial FexAl1-x/(In,Al)As/InP and III-V/FexAl1-x/(In,Al)As/InP structures." Journal of Vacuum Science & Technology B (Microelectronics and Nanometer Structures) 17, no. 3,
  • Clevenger, M. B.; Murray, C. S.; Ringel, S. A.; Sacks, R. N.; Qin, L.; Charache, G. W.; Depoy, D. M., 1999, "Optical properties of thin semiconductor device structures with reflective back-surface layers." AIP Conference Proceedings no. 460,
  • Kwon, D.; Kaplar, R. J.; Ringel, S. A.; Allerman, A. A.; Kurtz, S. R.; Jones, E. D., 1999, "Deep levels in p-type InGaAsN lattice matched to GaAs." Applied Physics Letters 74, no. 19,
  • Hierro, A.; Kwon, D.; Goss, S. H.; Brillson, L. J.; Ringel, S. A.; Rubini, S.; Pelucchig, E.; Franciosi, A., 1999, "Evidence for a dominant midgap trap in n-ZnSe grown by molecular beam epitaxy." Applied Physics Letters 75, no. 6,
  • Xu, Q.; Hsu, J. W. P.; Carlin, J. A.; Sieg, R. M.; Boeckl, J. J.; Ringel, S. A., 1999, "Topographic and electronic studies of wedge-shape surface defects on AlGaAs/GaAs films grown on Ge substrates." Applied Physics Letters 75, no. 14,

1998

  • Xu, Q.; Hsu, J. W. P.; Ting, S. M.; Fitzgerald, E. A.; Sieg, R. M.; Ringel, S. A., 1998, "Scanning force microscopy studies of GaAs films grown on offcut Ge substrates." Journal of Electronic Materials 27, no. 9,
  • Carlin, J. A.; Ringel, S. A.; Sacks, R. N.; Yap, K. S., 1998, "Role of Al content on surface structure evolution of low temperature AlxGa1-xAs and its effect on critical thickness." Journal of Vacuum Science & Technology B (Microelectronics and Nanometer Structures) 16, no. 3,
  • Ting, S. M.; Fitzgerald, E. A.; Sieg, R. M.; Ringel, S. A., 1998, "Range of defect morphologies on GaAs grown on offcut (001) Ge substrates." Journal of Electronic Materials 27, no. 5,
  • Ringel, S. A.; Chatterjee, B., 1998, "Electrical deactivation of interstitial Zn in heteroepitaxial InP by hydrogen and its effect on electronic properties." Journal of Applied Physics 83, no. 11,
  • Sieg, R. M.; Ringel, S. A.; Ting, S. M.; Samavedam, S. B.; Currie, M.; Langdo, T.; Fitzgerald, E. A., 1998, "Toward device-quality GaAs growth by molecular beam epitaxy on offcut Ge/Si1-xGex/Si substrates." Journal of Vacuum Science & Technology B (Microelectronics and Nanometer Structures) 16, no. 3,
  • Anderson, B. L.; Pelz, L. J.; Ringel, S. A.; Clymer, B. D.; Collins, S. A. , Jr., 1998, "Photonics laboratory with emphasis on technical diversity." IEEE Transactions on Education 41, no. 3,
  • Sieg, R. M.; Ringel, S. A.; Ting, S. M.; Fitzgerald, E. A.; Sacks, R. N., 1998, "Anti-phase domain-free growth of GaAs on offcut (001) Ge wafers by molecular beam epitaxy with suppressed Ge outdiffusion." Journal of Electronic Materials 27, no. 7,
  • Sieg, R. M.; Carlin, J. A.; Ringel, S. A.; Currie, M. T.; Ting, S. M.; Langdo, T. A.; Taraschi, G.; Fitzgerald, E. A.; Keyes, B. M., 1998, "High minority-carrier lifetimes in GaAs grown on low-defect-density Ge/GeSi/Si substrates." Applied Physics Letters 73, no. 21,

1997

  • Ringel, S. A.; Chatterjee, B.; Hoffman, R. W. , Jr., 1997, "Hydrogen passivation of interstitial Zn defects in hetero-epitaxial InP cell structures and influence on device characteristics." Progress in Photovoltaics: Research and Applications 5, no. 6,
  • Hoffman, R. W.; Fatemi, N. S.; Weizer, V. G.; Jenkins, P. P.; Stan, M. A.; Ringel, S. A.; Scheiman, D. A.; Wilt, D. M.; Brinker, D. J., 1997, "High beginning-of-life efficiency p/n InP solar cells." Progress in Photovoltaics: Research and Applications 5, no. 6,
  • Ringel, S. A., 1997, "Hydrogen-extended defect interactions in heteroepitaxial InP materials and devices." Solid-State Electronics 41, no. 3,
  • Sieg, R. M.; Sacks, R. N.; Ringel, S. A., 1997, "Application of pyrometric interferometry to the in situ monitoring of In0.52Al0.48As, In0.53Ga0.47As, and quaternary alloy growth on InP substrates." Journal of Crystal Growth 175-176,

1996

  • Chatterjee, B.; Ringel, S. A., 1996, "Effect of extended defects on the formation and dissociation kinetics of Zn-H complexes in heteroepitaxial p-type InP layers." Applied Physics Letters 69, no. 6,
  • Grillot, P. N.; Ringel, S. A., 1996, "Identification of compositionally invariant deep levels introduced by plastic strain in epitaxial Ge0.30Si0.70 and deformed bulk Si." Applied Physics Letters 69, no. 14,
  • Grillot, P. N.; Ringel, S. A.; Fitzgerald, E. A., 1996, "Effect of composition on deep levels in heteroepitaxial GexSi1-x layers and evidence for dominant intrinsic recombination-generation in relaxed Ge layers on Si." Journal of Electronic Materials 25, no. 7,
  • Grillot, P. N.; Ringel, S. A.; Michel, J.; Fitzgerald, E. A., 1996, "Structural, electronic, and luminescence investigation of strain-relaxation induced electrical conductivity type conversion in GeSi/Si heterostructures." Journal of Applied Physics 80, no. 5,
  • Sacks, R. N.; Sieg, R. M.; Ringel, S. A., 1996, "Investigation of the accuracy of pyrometric interferometry in determining AlxGa1-xAs growth rates and compositions." Journal of Vacuum Science & Technology B (Microelectronics and Nanometer Structures) 14, no. 3,
  • Chatterjee, B.; Ringel, S. A.; Hoffman, R. , Jr., 1996, "Hydrogen passivation of n+p and p+n heteroepitaxial InP solar cell structures." Progress in Photovoltaics: Research and Applications 4, no. 2,
  • Sieg, R. M.; Ringel, S. A., 1996, "Reabsorption, band-gap narrowing, and the reconciliation of photoluminescence spectra with electrical measurements for epitaxial n-InP." Journal of Applied Physics 80, no. 1,

1995

  • Mena, R. A.; Schacham, S. E.; Haugland, E. J.; Alterovitz, S. A.; Young, P. G.; Bibyk, S. B.; Ringel, S. A., 1995, "Characterization of the transport properties of channel delta-doped structures by light-modulated Shubnikov-de Haas measurements." Journal of Applied Physics 78, no. 11,
  • Grillot, P. N.; Ringel, S. A.; Fitzgerald, E. A.; Watson, G. P.; Xie, Y. H., 1995, "Electron trapping kinetics at dislocations in relaxed Ge0.3Si0.7/Si heterostructures." Journal of Applied Physics 77, no. 7,
  • Sieg, R. M.; Chatterjee, B.; Ringel, S. A., 1995, "Evidence for enhanced zinc interstitial concentration in strain-relaxed heteroepitaxial indium phosphide." Applied Physics Letters 66, no. 23,
  • Chatterjee, B.; Ringel, S. A., 1995, "Hydrogen passivation and its effects on carrier trapping by dislocations in InP/GaAs heterostructures." Journal of Applied Physics 77, no. 8,
  • Grillot, P. N.; Ringel, S. A.; Fitzgerald, E. A.; Watson, G. P.; Xie, Y. H., 1995, "Minority- and majority-carrier trapping in strain-relaxed Ge0.3Si0.7/Si heterostructure diodes grown by rapid thermal chemical-vapor deposition." Journal of Applied Physics 77, no. 2,
  • Mena, R. A.; Schacham, S. E.; Haugland, E. J.; Alterovitz, S. A.; Bibyk, S. B.; Ringel, S. A., 1995, "Subband quantum scattering times for AlGaAs/GaAs obtained using digital filtering." Journal of Applied Physics 78, no. 6,

1994

  • Chatterjee, B.; Ringel, S. A.; Sieg, R.; Hoffman, R.; Weinberg, I., 1994, "Hydrogen passivation of dislocations in InP on GaAs heterostructures." Applied Physics Letters 65, no. 1,

1991

  • Ringel, S. A.; Rohatgi, A., 1991, "The effects of trap-induced lifetime variations on the design and performance of high-efficiency GaAs solar cells." IEEE Transactions on Electron Devices 38, no. 11,
  • Rohatgi, A.; Sudharsanan, R.; Ringel, S. A.; MacDougal, M. H., 1991, "Growth and process optimization of CdTe and CdZnTe polycrystalline films for high efficiency solar cells." Solar Cells 30, no. 1-4,
  • Ringel, S. A.; Smith, A. W.; MacDougal, M. H.; Rohatgi, A., 1991, "The effects of CdCl2 on the electronic properties of molecular-beam epitaxially grown CdTe/CdS heterojunction solar cells." Journal of Applied Physics 70, no. 2,

1990

  • Ringel, S. A.; Sudharsanan, R.; Rohatgi, A.; Carter, W. B., 1990, "A study of polycrystalline Cd(Zn,Mn)Te/CdS films and interfaces." Journal of Electronic Materials 19, no. 3,
  • Ringel, S. A.; Sudharsanan, R.; Rohatgi, A.; Owens, M. S.; Gillis, H. P., 1990, "Effects of annealing and surface preparation on the properties of polycrystalline CdZnTe films grown by molecular beam epitaxy." Journal of Vacuum Science & Technology A (Vacuum, Surfaces, and Films) 8, no. 3,

1989

  • Ringel, S. A.; Rohatgi, A.; Tobin, S. P., 1989, "An approach toward 25-percent efficient GaAs heteroface solar cells." IEEE Transactions on Electron Devices 36, no. 7,
  • Rohatgi, A.; Ringel, S. A.; Sudharsanan, R.; Meyers, P. V.; Liu, C. H.; Ramanathan, V., 1989, "Investigation of polycrystalline CdZnTe, CdMnTe, and CdTe films for photovoltaic applications." Solar Cells 27, no. 1-4,

1988

  • DeWald, A. B.; Frost, R. L.; Ringel, S. A.; Schaffer, J. P.; Rohatgi, A.; Nielsen, B.; Lynn, K. G., 1988, "Positron annihilation spectroscopy of AlGaAs/GaAs interfaces in metalorganic chemical vapor deposition grown GaAs heterojunction solar cells." Journal of Vacuum Science & Technology A (Vacuum, Surfaces, and Films) 6, no. 4,
  • Rohatgi, A.; Ringel, S. A.; Welch, J.; Meeks, E.; Pollard, K.; Erbil, A.; Summers, C. J.; Meyers, P. V.; Liu, C. H., 1988, "Growth and characterization of CdMnTe and CdZnTe polycrystalline thin films for solar cells." Solar Cells 24, no. 1-2,

1987

  • Ringel, S. A.; Ashok, S., 1987, "Silicon surface barrier modification by low-energy nitrogen ion implantation." Journal of the Electrochemical Society 134, no. 6,

1986

  • Ashok, S.; Ringel, S. A., 1986, "Low-energy hydrogen implantation for silicon Schottky barrier modification." Vacuum 36, no. 11-12,
  • Ringel, S. A.; Mu, X. C.; Fonash, S. J.; Ashok, S., 1986, "A study of target heating in low-energy ion-beam processing." Journal of Vacuum Science & Technology A (Vacuum, Surfaces, and Films) 4, no. 5,
  • Giewont, K.; Ringel, S. A.; Ashok, S., 1986, "Synergistic effects in ion bombardment modification of silicon Schottky contacts." Journal of Vacuum Science & Technology A (Vacuum, Surfaces, and Films) 4, no. 3,
  • Ringel, S. A.; Chien, H. C.; Ashok, S., 1986, "Evidence for the formation of polycrystalline silicon by argon implantation and its passivation by atomic hydrogen." Applied Physics Letters 49, no. 12,