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Steven Ringel

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



Steven A. Ringel is the Neal Smith Endowed Chair Professor in the Department of Electrical and Computer Engineering at The Ohio State University.  He is also the founding and current Executive Director of The Ohio State University Institute for Materials Research (IMR), and he is the Faculty Director of Ohio State’s Materials and Manufacturing for Sustainability (M&MS) Discovery Theme.  IMR is Ohio State’s largest non-medical research center, with more than 200 faculty members from 22 academic departments in 5 colleges, performing more than $75M in annual research on a base of awards valued at more than $400M.  Within the IMR umbrella are state-of-the-art core facility centers, national centers of excellence and industry-university consortia.  The M&MS Discovery Theme is a paradigm-shifting effort at Ohio State to create pre-eminence in materials and technologies for sustainability, focusing on innovation and industry deployment.  

Professor Ringel is internationally recognized for his seminal contributions and leadership in the field of electronic materials and devices, particularly in photovoltaics, defect characterization techniques, wide bandgap semiconductors, and compound semiconductor-silicon integration. Specific to photovoltaics (PV), Dr. Ringel has spent much of his career making high impact contributions; his early work on CdTe solar cells revealed basic mechanisms behind the now standard cadmium chloride treatment applied in this global technology, his efforts in space PV resulted in the highest performance InP space solar cells at the time, and his group is world-recognized for its advancement of PV based on III-V/SiGe materials.  More recently, his group has produced the first large area, III-V/active-Si tandem and triple junction cells, translating these high-performance, low-cost technologies to industry. Dr. Ringel’s general focus on materials defects, their characterization and growth mitigation strategies have similarly made lasting impact on wide bandgap device technologies, including the invention of deep level optical spectroscopy methods that have been adopted by industry to solve GaN reliability issues. As co-founder and editor of the IEEE J-PV, the General Chair of the 2015 42nd IEEE PVSC and the former Chair of the international IEEE Photovoltaics Technical Committee, Dr Ringel has helped to define future directions in PV research and education.  

Professor Ringel has authored and co-authored more than 300 technical articles and conference presentations, given more than 120 invited talks, and has authored or edited 4 books and numerous chapters. At OSU he has produced more than 70 PhD and MS students. His recognitions include the 1994 NSF National Young Investigator Award, the Ohio State Distinguished Scholar Award, the Ohio State Scott Award for Outstanding Academic Achievement in Engineering, the OSU Harrison Award for Excellence in Engineering, seven best paper awards from international conferences and societies, AAAS Fellow and AIAA Associate Fellow. He sits on several international boards (Tyndall Institute in Ireland, Singapore-MIT Alliance for Research and Technology (SMART) - for which he is chair of the LEES IRG board, and the Sandia National Labs UWBG center), he has been a visiting professor numerous times (UPM-Spain, NTU-Singapore, Cardiff),  and he is a co-founder of several startup companies. Dr. Ringel received his Ph.D. degree in Electrical Engineering from Georgia Tech in 1991, and his M.S. and B.S. degrees from Penn State in 1986 and 1984, respectively. 


Ph.D. 1991, Georgia Institute of Technology

Research Interests

Electronic materials and devices, photovoltaics, defect engineering, epitaxy and innovation in defect characterization methods; Broad interests in the science and application of electronic materials for applications in energy, electronics and optoelectronic technologies; Defect engineering in semiconductors and development of methods for trap spectroscopy; with applications to wide bandgap semiconductor devices and new materials; Substrate engineering; heterogeneous integration and interface science; The academic-industry research interface; Translational materials and its role in global innovation in solar energy, next generation electronics and general technology development.


375 Caldwell Laboratory

Personal website


  • 20150601

    Advisor, Best Student Paper Award: Zeng Zhang.

  • 20150201

    Distinguished Scholar Award.

  • 20140301

    Honorary Professor.

  • 20140101

    Member, Advisory Board.

  • 20140101

    Chair, Scientific Advisory Board/Visiting Committee.

  • 20130401

    Invited Tutorial Speaker.

  • 20120101

    Clara M. and Peter L. Scott Award for Outstanding Achievement.

  • 20100201

    Lumley Research Award.

  • 20040101-20090101

    Invited Guest Lecturer.

  • 20080101

    Visiting Professor.

  • 20080101

    Co-investigator of Clean Energy Research Program.

  • 20080101

    Associate Fellow.

  • 20070701

    Invited Tutorial Speaker. University of Saint Francis.

  • 20050201

    Lumley Research Award.

  • 20050101

    AAAS Fellow.

  • 20040101

    Advisor, MRS Gold Medal Student Award: A. Armstrong.

  • 20040101

    Neal A. Smith Endowed Chair.

  • 20030601

    Advisor, Best Student Paper Award: O. Kwon.

  • 20010601

    Advisor, Best Student Paper Award: R. Kaplar.

  • 20001101

    Advisor, MRS Gold Medal Student Award: A. Hierro.

  • 20000201

    Lumley Research Award.

  • 19990201

    Stanley F. Harrison Faculty Award for Excellence in Engineering Research & Education.

  • 19990101

    Stanley E. Harrison Faculty Award for Excellence in Engineering.

  • 19940101

    National Young Investigator Award.

Edited Books


  • Schwarz, R.B., Ceder, G., Ringel, S.A.. 2002. "Materials for Energy Storage, Generation and Transport." Materials Research Society Press.


  • S.A. Ringel, S.A., Fitzgerald, E.A., Adesida, I., Houghton, D.. 1999. "III-V and IV-IV Materials and Processing Challenges for Highly Integrated Microelectronics and Optoelectronics." Materials Research Society Press.


  • Buckley, D.N., Ringel, S.A., Ren, F.. 1995. "Symposium on Large Area Wafer Growth and Processing for Electronic and Photonic Devices and the Twentieth State of the Art Program on Compound Semiconductors." The Electrochemical Society Press.



  • 2010. "The III-V solar cell on Silicon." In III-V Compound Semiconductors: Integration with Silicon-Based Microelectronics, edited by Li, T., E. Piner, E., Dadgar, A.,


  • 1998. "Electronic Properties and Deep Levels in Germanium-Silicon." In Semiconductors and Semimetals, edited by Bean, J., Hull, R.,


  • 1997. "Hydrogenation of Compound Semiconductors." In Processing Technology for Semiconductors, edited by Pearton, SJ,

Journal Articles


  • Xuan Sang Nguyen,X,S; Goh,Xuan,Long; Zhang,Li; Zhang,Zeng; Arehart,Aaron,R; Ringel,Steven,A; Fitzgerald,Eugene,A; Chua,Soo,Jin, 2016, "Deep level traps in GaN LEDs grown by metal organic vapour phase epitaxy on an 8 inch Si(111) substrate." JAPANESE JOURNAL OF APPLIED PHYSICS 55, no. 6, 060306 - 060306.


  • Sasikumar,A; Arehart,A,R; Via,G,D; Winningham,B; Poling,B; Heller,E; Ringel,S,A, 2015, "Identification of an RF degradation mechanism in GaN based HEMTs triggered by midgap traps." MICROELECTRONICS RELIABILITY 55, no. 11, 2258-2262 - 2258-2262.


  • Chmielewski,Daniel,J; Grassman,Tyler,J; Carlin,Andrew,M; Carlin,John,A; Speelman,Austin,J; Ringel,Steven,A, 2014, "Metamorphic GaAsP Tunnel Junctions for High-Efficiency III-V/IV Multijunction Solar Cell Technology." IEEE JOURNAL OF PHOTOVOLTAICS 4, no. 5, 1301-1305 - 1301-1305.


  • Long,R,D; Jackson,C,M; Yang,J; Hazeghi,A; Hitzman,C; Majety,S; Arehart,A,R; Nishi,Y; Ma,T,P; Ringel,S,A; McIntyre,P,C, 2013, "Interface trap evaluation of Pd/Al2O3/GaN metal oxide semiconductor capacitors and the influence of near-interface hydrogen." APPLIED PHYSICS LETTERS 103, no. 20, 201607 - 201607.


  • Zhang,Z; Hurni,C,A; Arehart,A,R; Yang,J; Myers,R,C; Speck,J,S; Ringel,S,A, 2012, "Deep traps in nonpolar m-plane GaN grown by ammonia-based molecular beam epitaxy." APPLIED PHYSICS LETTERS 100, no. 5, 052114 - 052114.


  • Grassman,Tyler,J; Brenner,Mark,R; Gonzalez,Maria; Carlin,Andrew,M; Unocic,Raymond,R; Dehoff,Ryan,R; Mills,Michael,J; Ringel,Steven,A, 2010, "Characterization of Metamorphic GaAsP/Si Materials and Devices for Photovoltaic Applications." IEEE TRANSACTIONS ON ELECTRON DEVICES 57, no. 12, 3361-3369 - 3361-3369.


  • Yang,Chieh-Kai; Roblin,Patrick; Malonis,Andrew; Arehart,Aaron; Ringel,Steven; Poblenz,Christiane; Pei,Yi; Speck,James; Mishra,Umesh, 2009, "Characterization of Traps in AlGaN/GaN HEMTs with a Combined Large Signal Network Analyzer/Deep Level Optical Spectrometer System." 2009 IEEE/MTT-S INTERNATIONAL MICROWAVE SYMPOSIUM, VOLS 1-3 1-3, 1209-1212 - 1209-1212.
  • Grassman,T,J; Brenner,M,R; Rajagopalan,S; Unocic,R; DEHOFF,R; Mills,M; Fraser,H; Ringel,S,A, 2009, "Control and elimination of nucleation-related defects in GaP/Si(001) heteroepitaxy." APPLIED PHYSICS LETTERS 94, no. 23, 232106 - 232106.


  • Arehart,A,R; Corrion,A; Poblenz,C; Speck,J,S; Mishra,U,K; DenBaars,S,P; Ringel,S,A, 2008, "Comparison of deep level incorporation in ammonia and rf-plasma assisted molecular beam epitaxy n-GaN films." PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 6 5, no. 6, 1750-1752 - 1750-1752.
  • Smith,P,E; LUECK,M; Ringel,S,A; BRILLSON,L,J, 2008, "Atomic diffusion and interface electronic structure at In0.49Ga0.51P/GaAs heterojunctions." JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 26, no. 1, 89-95 - 89-95.


  • Mosbacker,H,L; El Hage,S; Gonzalez,M; Ringel,S,A; Hetzer,M; Look,D,C; Cantwell,G; Zhang,J; Song,J,J; BRILLSON,L,J, 2007, "Role of subsurface defects in metal-ZnO(0001) Schottky barrier formation." JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 25, no. 4, 1405-1411 - 1405-1411.
  • Smith,P,E; LUECK,M; Ringel,S,A; BRILLSON,L,J, 2007, "Atomic diffusion and electronic structure in Al0.52In0.48P/GaAs heterostructures." JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 25, no. 6, 1916-1921 - 1916-1921.


  • 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 2, no. 7, 2411-2414 - 2411-2414.
  • Armstrong,A; Green,D; Arehart,A,R; Mishra,U,K; Speck,J,S; Ringel,S,A, 2005, "Carbon-related deep states in compensated n-type and semi-insulating GaN : C and their influence on yellow luminescence." GAN, AIN, INN AND THEIR ALLOYS 831, 311-316 - 311-316.


  • Arehart,A,R; Poblenz,C; Heying,B; Speck,J,S; Mishra,U,K; DenBaars,S,P; Ringel,S,A, 2003, "Influence of growth parameters on the deep level spectrum in MBE-grown n-GaN." GAN AND RELATED ALLOYS - 2003 798, 735-740 - 735-740.
  • Armstrong,A; Arehart,A,R; Ringel,S,A; Moran,B; DenBaars,S,P; Mishra,U,K; Speck,J,S, 2003, "Identification of carbon-related bandgap states in GaN grown by MOCVD." GAN AND RELATED ALLOYS - 2003 798, 509-514 - 509-514.

Papers in Proceedings


  • Sasikumar,A; Arehart,A; Ringel,S,A; Kaun,S; Wong,M,H; Mishra,U,K; Speck,J,S "Direct Correlation Between Specific Trap Formation and Electric Stress-induced Degradation in MBE-grown AlGaN/GaN HEMTs." in IEEE International Reliability Physics Symposium (IRPS). (1 2012).