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Other Presentations

2017

  • (Invited) A. R. Arehart, S. Ringel, E. Farzana, Z. Zhang, E. Ahmadi, Y. Oshima, J. Speck, "Investigation of Schottky Contacts and Traps in β‐Ga2O3," PCSI, Santa Fe, NM (January 15-19, 2017)

2016

  • (Invited) S.A. Ringel, E. Farzana, Z. Zhang, and A.R. Arehart J.S. Speck, E. Ahmadi, Y. Oshima, S. Kaun, J. Hogan, F. Wu, and H. Okumura, “b-Ga2O3 Materials Characterization: Deep Levels and Schottky Barriers,” second DoD Beta Gallium Oxide Workshop, Arlington, VA December 11-12, 2016.

  • (Invited) S.A. Ringel, T.J. Grassman, J.A. Carlin and D. Chmielewski, “Si-Based Tandem and Triple Junction Solar Cells Using III-V Compounds,” Universidad Politecnica de Madrid, Madrid, Spain, 2016.

  • (Invited) S.A. Ringel, T.J. Grassman, J.A. Carlin and D. Chmielewski, “III-V/Si Tandem and Triple Junction Solar Cells,”International Conference on Elecronic Materials (I-UMRS), Singapore, 2016.

  • (Invited) S.A. Ringel, “Development of Epitaxial 2- and 3-junction III-V/Si Tandem Solar Cells,” Trina Solar and State Key Laboratory of Photovoltaic Science and Tchnology, Changzhou, China, May, 2016.

  • (Invited) S.A. Ringel, “Materials Science for III-V/Si Solar Cells,” Distinguished Lecture, Department of Materials Science and Engineering, University of Southern California, 2016.

  • (Invited) S.A. Ringel, “A Perspective on Emerging High Efficiency and Low Cost PV Technologies in U.S. R&D and Ohio State PV Efforts,” Solar Task Force – FICCI, Delhi, India, 2016

  • (Invited) S.A. Ringel, T.J. Grassman, D.J. Chmielewski and John A. Carlin, “Development of Epitaxial 2- and 3-Junction III-V/Si Solar Cells,” 43rd IEEE Photovoltaic Specialists Conference, Portland, OR, June 5-10, 2016.

  • (Invited) S.A. Ringel, “Trap Characterization in III-Nitride Alloys from InGaN to AlGaN,” Workshop on Compound Semiconductor Materials and Devices (WOCSEMMAD), Tucson, AZ, February 16-19, 2016.

  • (Invited) S.A. Ringel, A. Arehart, S. Rajan, J. Speck and G. Jessen,  “Traps in UWBGs and What to Do About Them: Characterization Challenges and Advantage of b-Ga2O3,” 2nd technology exchange on UWBG semiconductors, Arlington, VA, 2016.

  • (Invited) S.A. Ringel, A. Arehart, E. Farzana, E. Ahmadi, Y. Oshima and J. Speck, “Deep Traps in Wide Bandgap Semiconductors: From GaN to Beta Gallium Oxide,” AVS 63rd International Symposium and Exhibition, Nashville, TN USA, 2016.

2015

  • (INVITED) Steven A. Ringel, A.R. Arehart, Z. Zhang,1 E. Farzana, S. Kaun and J.S. Speck, "Quantitative Characterization of Deep Level Defects and Schottky Barriers in (010) ß-Ga2O3 Materials" presented at 1st Workshop on Beta Gallium Oxide (IWBGO), Kyoto Japan (November 2-6, 2015)

  • Kevin Galiano, Darryl Gleason, Pran Krishna Paul, Zeng Zhang, Drew Cardwell, Brian McSkimming, James Speck, Aaron Arehart, Steven Ringel, Jonathan Pelz , "Spatial Localization and Variation in Defect-Related Electron Traps in GaN Materials" presented at APS NMC/BP Conference, Miami, FL ( October 9–11, 2015).

  • Steven A. Ringel, Tyler J. Grassman, John A. Carlin, Andrew M. Carlin and Eugene A. Fitzgerald, "III-V/Si Multijunction Photovoltaics" presented at International Conference on Materials for Advanced Technologies (ICMAT 2015) Suntec Singapore (June 28 - July 03, 2015)

  • Christine M. Jackson, M. A. Negara, Aaron R. Arehart,Paul C. McIntyre, Steven A. Ringel, “Electrical Characterization of ALD TiO2/Al2O3 Bilayers on GaN”, presented at AVS 15th International Conference on Atomic Layer Deposition, Portland, OR (June 28 - July 1, 2015).

  • Paul, P.  K., D. W. Cardwell, C. M. Jackson, K. Galiano, K. Aryal, J. P. Pelz, S. Marsillac, S. A. Ringel, T. J. Grassman, and A. R. Arehart , “Relating the Ev+0.47 eV trap in CIGS to specific grain boundaries”, presented at MRS 57th Electronic Materials Conference, Columbus, OH (June 24-26, 2015).

  • Wenyuan Sun, C. M. Jackson, P. Paul, Z. Zhang, A. R. Arehart and S. A. Ringel, “Identification of Ec-0.9eV trap-induced VT shift in GaN/Si MISHEMTs”, presented at MRS 57th Electronic Materials Conference, Columbus, OH (June 24-26, 2015).

  • Zeng Zhang, E. Farzana, E. Kyle, N. Young, S. Keller, U. Mishra, J. Speck, A. Arehart and S. Ringel, “Deep Level States in p-type GaN Grown by Ammonia-based Molecular Beam Epitaxy and Metal Organic Chemical Vapor Deposition”, presented at MRS 57th Electronic Materials Conference, Columbus, OH (June 24-26, 2015). WON BEST PAPER AWARD

  • Christine M. Jackson, M. A. Negara, A. R. Arehart, P. C. McIntyre, S. A. Ringel, “Leakage Current and Interface States in Pd/TiO2/Al2O3/GaN Capacitors”, presented at MRS 57th Electronic Materials Conference, Columbus, OH (June 24-26, 2015).

  • Kevin Galiano, D. Gleason, P. Paul, Z. Zhang, D. Cardwell, B. McSkimming, J. Speck, A. Arehart, S. A. Ringel, J. Pelz, “Evidence for Spatial Localization of the EC-0.57 eV Trap in n-GaN”, presented at MRS 57th Electronic Materials Conference, Columbus, OH (June 24-26, 2015).

  • Esmat Farzana, Z. Zhang, E. C. H. Kyle, E. X. Zhang, D. M. Fleetwood, R. D. Shrimpf, J. S. Speck,A. R. Arehart, and S.A. Ringel, “Comparison of electron and proton irradiation-induced traps in n-type GaN”, presented at MRS 57th Electronic Materials Conference, Columbus, OH (June 24-26, 2015).

  • Tyler J. Grassman et al., “Advances in the Development of Epitaxial GaAsP/Si Dual-Junction Solar Cells,” presented at MRS 57th Electronic Materials Conference, Columbus, OH (June 24-26, 2015).

  • Julia I. Deitz et al., “Extending Characterization Applications of Electron Channeling Contrast Imaging,” presented at MRS 57th Electronic Materials Conference, Columbus, OH (June 24-26, 2015).

  • Daniel J. Chmielewski et al., “High-Performance Metamorphic Tunnel Junctions on Si for III‑V/Si Multijunction Solar Cells,” presented at MRS 57th Electronic Materials Conference, Columbus, OH (June 24-26, 2015).

  • (Invited Talk) Tyler J. Grassman et al., “Progress in the Development of Epitaxial GaAsP/Si Dual-Junction Solar Cells,” presented at 42nd IEEE Photovoltaic Specialists Conference, New Orleans, LA, (June 14-19, 2015).

  • Daniel J. Chmielewski et al., “High-Performance Metamorphic Tunnel Junctions on Si for III‑V/Si Multijunction Solar Cells,” presented at 42nd IEEE Photovoltaic Specialist Conference, New Orleans, LA (June 14-19, 2015).

  • Elisa García-Tabarés et al., “Evolution of the Silicon Bottom Cell Photovoltaic Behavior during III-V on Si Multi-junction Solar Cells Production,” presented at 42nd IEEE Photovoltaic Specialist Conference, New Orleans, LA, (June 14-19, 2015).

  • Drew W. Cardwell et al., “Investigations of Metamorphic (Al)GaInP for III-V Multijunction Photovoltaics,” presented at 42nd IEEE Photovoltaic Specialist Conference, New Orleans, LA (June 14-19, 2015).

  • Julia I. Deitz et al., “Extending Characterization Applications of Electron Channeling Contrast Imaging,” presented at 42nd IEEE Photovoltaic Specialist Conference, New Orleans, LA, (June 14-19, 2015).

  • (Invited Talk) Tyler J. Grassman et al., “Advances in III-V/Active-Silicon Multijunction Photovoltaics: Progress Toward a Si-Plus Architecture,” presented at 227th Electrochemical Society Meeting, Chicago, IL, (May 26, 2015).

  • (Invited Seminar) Tyler J. Grassman et al., “Advances in the Development of Epitaxial III-V/Si Multijunction Solar Cells,” presented at Case Western Reserve University (Dept. of Electrical Engineering and Computer Science), (March 17, 2015).

  • Aaron R. Arehart, W. Sun, A. Sasikumar and S. A. Ringel, “Ec-2.0eV trap related GaN/Si MISHEMTs dynamic Ron degradation”, presented at CS ManTech, Scottsdale, AZ (2015).

  • Anup Sasikumar, Z. Zhang, P. Kumar, E. X. Zhang, D. M. Fleetwood, R. D. Schrimpf, P. Saunier, C. Lee, S. A. Ringel, andA. R. Arehart, “Proton irradiation-induced traps causing VT instabilities and RF degradation in GaN HEMTs”, presented at IEEE Intl. Reliab. Phys. Symp. Monterey, CA (April 19-23, 2015).

  • Zeng Zhang, A. Arehart, E. C. H. Kyle,J. Chen, E. Zhang, D. M. Fleetwood, R. D. Shrimpf, J. Speck and S.A. Ringel, “Proton Irradiation Effects on Deep Level States in P-type GaN” presented at Spring Materials Research Society Meeting, San Francisco, CA (April 6-10, 2015).

  • (INVITED) Steven A. Ringel, A. R. Arehart, Z. Zhang, A. Sasikumar, D. Cardwell, E. C. H. Kyle, S. Kaun, J. Chen, E.X. Zhang, P. Saunier, C. Lee,D.M. Fleetwood, R.D. Schrimpf, and J.S. Speck “Toward an Understanding of GaN Defects and Device Reliability Using Deep Level Trap Spectroscopy Methods”, presented at Spring Materials Research Society Meeting, San Francisco, CA (April 6-10, 2015).

  • Anup Sasikumar, Z. Zhang, P. Kumar, E. X. Zhang, D. M. Fleetwood, R. D. Schrimpf, P. Saunier, C. Lee, S. A. Ringel, and A. R. Arehart, “Comparison of Irradiation and Electrical Stressors on AlGaN/GaN HEMT Reliability”, presented at the Government Microcircuit Applications and Critical Technology Conference, St. Louis, MO (March 23-26, 2015).

  • (INVITED) “Experiences in Early Stage Private R&D as a University Professor,” S.A. Ringel, presented at Workshop on Compound Semiconductor Materials and Devices (WOCSEMMAD), Charleston, SC (February 16-19, 2015).

2014

  • Zeng Zhang, D. Cardwell, A. Sasikumar, A. R. Arehart, E. C. H. Kyle, E. Zhang, D. M. Fleetwood, R. D. Shrimpf, J. S. Speck and S.A. Ringel, “Impact of the GaN Buffer on Proton-Radiation Induced Threshold Voltage Shifts in AlGaN/GaN Heterostructures”, presented at Fall Materials Research Society Meeting, Boston, MA (2014).

  • Steven A. Ringel, A. Sasikumar, Z. Zhang, C. Jackson, A. R. Arehart, S. W. Kaun, J. S. Speck, J. Chen, E. Zhang, D. Fleetwood, and R. Schrimpf, “Defects in GaN based transistors,” presented at SPIE Photonics West, San Francisco, CA (2014).

  • Anup Sasikumar, A. R. Arehart, S. A. Ringel, “High voltage trap spectroscopy and applications to GaN-on-Si power HEMTs,” presented at WOCSEMMAD, San Antonio, TX (2014).

  • Anup Sasikumar, D. W. Cardwell, A. R. Arehart, J. Lu, S. Keller, U. K. Mishra, J. S. Speck, J. P. Pelz, and S. A. Ringel, “Toward a physical understanding of the reliability-limiting EC-0.57 eV trap in GaN HEMTs,” presented at the IEEE Intl. Reliab. Phys. Symp., Waikoloa, HI (June 3-5, 2014).

  • Tyler J. Grassman et al., “Rapid Extended Defect Characterization in Semiconductor Heterostructures by Electron Channeling Contrast Imaging,” presented at Space Photovoltaic Research and Technology Conference XXIII, Cleveland, OH (October 2014).

  • Drew W. Cardwell et al., “Metamorphic and Lattice-Matched Wide-Gap AlGaInP-based Top-Cell Materials and Cells for III-V Multijunction Photovoltaics,” presented at 23rd Space Photovoltaics Research and Technology Conference, Cleveland, OH (Oct 28-30, 2014).

  • Julia I. Deitz et al., “Using Electron Channeling Contrast Imaging for Misfit Dislocation Characterization in Heteroepitaxial III-V/Si Thin Films,” presented at 2014 Microscopy & Microanalysis, Hartford, CT (Aug 3-7, 2014).

  • (Invited Talk) Steven A. Ringel et al., “Defects in Photovoltaics: III-V/Si Multijunction Solar Cells,” presentd at Gordon Research Conference (Defects in Semiconductors: Power, Efficiency, and Functionality), Waltham, MA (Aug 3-8, 2014).

  • Santino D. Carnevale, J. I. Deitz, J. A. Carlin, Y. N. Picard, M. De Graef, S. A. Ringel, T. J. Grassman, “Rapid Characterization of Extended Defects in III-V/Si by Electron Channeling Contrast Imaging,” presented at the 40th IEEE Photovoltaic Specialists Conference, 2800 (2014).

  • Chris Ratcliff, T. J. Grassman, J. A. Carlin, D. J. Chmielewski, S. A. Ringel, "Ga-rich GaxIn1-xP solar cells on Si with 1.95 eV bandgap for ideal III-V/Si photovoltaics," presented at SPIE 8981: Physics, Simulation, and Photonic Engineering of Photovoltaic Devices III, 898118 (2014).

  • James S. Speck, Z. Zhang, A. R. Arehart, E. Cinkilic, J. Chen, E. X. Zhang, Y. S. Puzyrev, C. X. Zhang, M. W. McCurdy, S. T. Pantelides, B. McSkimming, S. W. Kaun, E. C. H. Kyle, D. M. Fleetwood, R. D. Schrimpf, S. A. Ringel, “Proton Irradiation in Bulk GaN Layers and Nitride-based HEMT Devices,” presented at the Govt. Microcircuit Appl. Critical Tech. Conf. (GOMACTech) (2014).