Publication/Press Release List

 

Books Edited

  • R.B. Schwarz, G. Ceder and S.A. Ringel, "Materials for Energy Storage, Generation and Transport," vol. 730 (Materials Research Society Press, 2002).

  • S.A. Ringel, E.A. Fitzgerald, I. Adesida, D. Houghton, "III-V and IV-IV Materials and Processing Challenges for Highly Integrated Microelectronics and Optoelectronics,"  vol. 535 (Materials Research Society Press, 1999).

  • D.N. Buckley, S.A. Ringel and F. Ren, editors, "Symposium on Large Area Wafer Growth and Processing for Electronic and Photonic Devices and the Twentieth State of the Art Program on Compound Semiconductors, 185th Meeting of the Electrochemical Society, San Francisco, CA 1994 (The Electrochemical Society Press, Pennington, NJ, 1995).


Inivited Book Chapters

  • S.A. Ringel and P.N. Grillot, "Electronic Properties and Deep Levels in Germanium-Silicon," in Germanium-Silicon, Vol. 56 of Semiconductors and Semimetals,ed. by J. Bean and R. Hull, pp. 293-346 (Academic Press, 1999).

  • S.A.Ringel and B. Chatterjee, "Hydrogenation of Compound Semiconductors,"in Processing Technology for Semiconducctors, ed. by S.J.Pearton, pp. 243-263 (Research Signpost Publications, India, 1997).


Patents Issued

  • S.A. Ringel, B. Chatterjee and R. Hoffman, Jr., "Hydrogen Passivated Heteroepitaxial III-V Photovoltaic Devices Grown on Lattice-Mismatched Substrates, and Process," U.S. patent no. 5,571,339, Nov. 5 1996.


Refereed Journal Articles in Print

  • D. Liu, M.K. Hudait, Y. Lin, J. Kim, S.A. Ringel, and W. Lu, "Gate length scaling study of InAlAs/InGaAs/InAsP composite channel HEMTs," Solid State Electronics 51, 838-841 (2007).

  • A.R. Arehart, C. Poblenz, J.S. Speck, U.K. Mishra, S.P. DenBaars, and S.A. Ringel, "Comparison of deep level incorporation in ammonia and rf-plasma assisted molecular beam epitaxy n-GaN films," Phys. Stat. Sol. A., accepted and to appear, (2007).

  • A. Armstrong, J. Caudill, C. Poblenz, A. Carrion, U.K. Mishra, J.S. Speck, and S.A. Ringel, "Characterization of majority and minoirty carrier deep levels in p-type GaN:Mg grown by molecular beam epitaxy using deep level optical spectroscopy," accepted and to appear, J. Appl. Physics (2007).

  • P.E. Smith, M. Lueck, S.A. Ringel, and L.J. Brillson, "Atomic Diffusion and Interface Electronic Structure at In0.49Ga0.51P/GaAs Heterojunctions," accepted and to appear, J. Vac. Sci. Technol. B (2007).

  • P.E. Smith, M. Lueck, S.A. Ringel, and L.J. Brillson, "Atomic Diffusion and Interface Electronic Structure at Al0.52In0.48P/GaAs Heterojunctions," J. Vac. Sci. Technol. B 25, 1916-1921 (2007).

  • A. Armstrong, A. Corrion, C. Poblenz, U.K. Mishra, J.S. Speck, and S.A. Ringel, "Comparison of deep level spectra in p-type and n-type GaN grown by molecular beam epitaxy," Phys. Stat. Sol. B., 244, 1867-1871 (2007).

  • Y. Lin, J.A. Carlin, A. Arehart, A.M. Carlin, and S.A. Ringel, "High mobility two-dimensional electron gas in InAlAs/InAs heterostructures grown on virtual InAs substrates by molecular beam epitaxy," Appl. Phys. Lett. 90, 012115:1-3 (2007).

  • H.L. Mosbacker, S. El Hage, M. Gonzalez, S.A. Ringel, M. Hetzer, D.C. Look, G. Cantwell, J. Zhang, J.J. Song, and L.J. Brillson, "Role of Subsurface Defects in Metal-ZnO[000(-l)] Schottky Barrier Formation," J. Vac. Sci. Techol. B 24, 1405-1411 (2007).

  • A. Armstrong, A.Chakroborty, J.S. Speck, S.P. DenBaars, U.K. Mishra, and S.A. Ringel, "Quantitative observation and discrimination of AlGaN- and GaN-related deep levels in AlGaN/GaN heterostructures using capacitance deep level optical spectroscopy," Appl. Phys. Lett. 89, 262116:1-3 (2006).

  • M.K. Hudait, P.M. Sinha, J.R. Lindenmuth, and S.A. Ringel, "Carrier compensation and scattering mechanisms in Si-doped InAsyP1-y layers grown on InP substrates using intermediate InAsyP1-y step-graded buffers," J. Appl. Phys. Lett. 100, 063705:1-9 (2006).

  • A. Arehart, B. Moran, J.S. Speck, U.K. Mishra, and S.P.DenBaars, and S.A. Ringel, "Effect of threading dislocation density on Ni/n-GaN Schottky diode I-V characteristics," J. Appl. Phys. Lett. 100, 023709:1-8 (2006).

  • O. Kwon, J.J. Boeckl, M.L. Lee, A.J. Pitera, E.A. Fitzgerald, and S.A. Ringel, "Monolithic integration of AlGaInP laser diodes on SiGe/Si substrates by mlecular beam epitaxy," J. Appl. Phys. Lett. 100, 013103:1-7 (2006).

  • D. Liu, M.K.Hudait, Y. Lin, J. Kim, S.A. Ringel, and W. Lu, "InGaAs/InAsP composite channel high electron mobility transistors," Electronics Letters 42, (2006).

  • M. Gonzalez, C.L. Andre, R.J. Walters, S.R. Messenger, J.H. Warner,J.R. Lorentzen, A.J. Pitera, E.A. Fitzgerald and S.A. Ringel, "Deep level defects in proton radiated GaAs grown on metamorphic SiGe/Si substrates," J. Appl. Phys. Lett. 100, 034503:1-7 (2006).

  • A. Armstrong, C. Poblenz, D.S. Green, U.K. Mishra, J.S. Speck and S.A. Ringel, "Impact of Substrate Temperature on the Incorporatoin of Carbon-Related Defects and Mechanism for Semi-Insulating Behavior in GaN Grown by Molecular Beam Epitaxy," Appl. Phys. Lett. 88, 082114:1-3 (2006).

  • M. Lueck, C.L. Andre, A.J. Pitera, M.L. Lee, E.A. Fitzgerald and S.A. Ringel, Dual Junction InGaP/GaAs Solar Cells Grown on Metamorphic SiGe Substrates," IEEE Electron Devices Letters 27, 142-144 (2006).

  • A. Armstrong, A.R. Arehart, D. Green, U.K. Mishra, J.S. Speck and S.A. Ringel, Impact of Deep Levels on the Electrical Conductivity and Luminescence of Gallium Nitride Co-Doped with Carbon and Silicon, " J. Appl. Phys. 98, pp. 053704:1-11 (2005).

  • C.L. Andre, D.M. Wilt, A.J. Pitera, M.L. Lee, E.A. Fitzgerald and S.A. Ringel, Comparative Impact of Dislocation Densities on n+p and p+n Junction GaAs Diodes and Solar Cells on SiGe Virtual Substrates," J. Appl. Phys. 98, pp. 014502: 1-5(2005).

  • P.E. Smith, S.H. Goss, M. Gao, M.K. Hudait, Y. Lin, S.A. Ringel and L.J. Brillson, Atomic Diffusion and Band Lineups at the In0.53Ga0.47As-on-InP Heterointerfaces," J. Vac. Sci. Technol. B 23, ppl. 1832-1837 (2005).

  • O. Kwon, Y. Lin, J.J. Boeckl and S.A. Ringel, Properties of digitally-alloyed AlGaInP grown by solid source molecular beam epitaxy," J. Electron. Mater. 34, pp. 1-6 (2005)

  • C.L. Andre, J.A. Carlin, J.J. Boeckl, D.M. Wilt, M.A. Smith, A.J. Pitera, M.L. Lee, E.A. Fitzgerald, and S.A. Ringel, Investigations of high performance GaAs solar cells grown on Ge-SiGe-Si substrates," IEEE Trans. El. Dev. 52, pp. 1055-1060 (2005).

  • M. Gao, Y. Lin, S.T. Bradley, S.A. Ringel, J. Hwang, W.J. Schaff and L.J. Brillson, Spontaneous Compositional Superlattice and Band-Gap Reduction in Si-doped AlxGa1-xN Epilayers," Appl. Phys. Lett. 87, pp. 191906:1-3 (2005).

  • M.K. Hudait, Y. Lin, S.H. Goss, P. Smith, S. Bradley, L.J. Brillson, S.W. Johnston, R.K. Ahrenkiel and S.A. Ringel, Evidence of interface-induced persistent photoconductivity in InP/In0.53Ga0.47As/InP double heterostructures grown by molecular beam epitaxy," Appl. Phys. Lett. 87, pp. 032106: 1-3 (2005).

  • Y. Lin, M.K. Hudait, S.W. Johnston, R.K. Ahrenkiel and S.A. Ringel, Photoconductivity Decay Study of Metamorphic InAsP/InGaAs Heterostructures Grown by Molecular Beam Epitaxy," Appl. Phys. Lett. 86, pp. 071908: 1-3 (2005).

  • A. Armstrong, A.R. Arehart and S.A. Ringel, A Method to Determine Deep Level Profiles in Highly Compensated, Wide Bandgap Semiconductors," J. Appl. Phys. 97, 083529:1-6 (2005).

  • A. Armstrong, A. Arehart, D. Green, J.S. Speck, U.K. Mishra and S.A. Ringel, A Novel Method to Investigate Defect States in MBE-Grown Highly Resistive GaN Doped with C and Si," Phys. Stat. Sol. C Vol. 13 (1), pp. 1-5 (2005).

  • O. Kwon, J.J. Boeckl, M.L. Lee, A.J. Pitera, E.A. Fitzgerald and S.A. Ringel, Growth and Properties of AlGaInP Resonant Cavity Light Emitting Diodes on Ge/SiGe/Si Substrates," J. Appl. Phys. 97, pp. 1-6 (2005).

  • P.E. Smith, S.H. Goss, S.T. Bradley, M.K. Hudait, Y. Lin and S.A. Ringel, Atomic Layer Diffusion and Electronic Structure at In0.53Ga0.47As/InP Interfaces," Appl. Phys. Lett. J. Vac. Sci. and Technol. B 22, pp. 554-559 (2004).

  • C.L. Andre, J.J. Boeckl, D.M. Wilt, A.J. Pitera, M.L. Lee, E.A. Fitzgerald, B.M. Keyes and S.A. Ringel, Impact of dislocations on minority carrier electron and hole lifetimes in GaAs grown on metamorphic SiGe substrates," Appl. Phys. Lett. 84, pp. 3447-3449 (2004).

  • A. Armstrong, A. Arehart, B. Moran, S.P. DenBaars, U.K. Mishra, J. Speck and S.A. Ringel, Impact of Carbon on Trap States in n-type GaN Grown by Metalorganic Chemical Vapor Deposition," Appl. Phys. Lett. 84, pp. 374-376 (2004).

  • M.K. Hudait, Y. Lin, M.N. Palmisiano, C. Tivarus, J.P. Pelz and S.A. Ringel, Comparison of mixed anion InAsP and mixed cation InAlAs metamorphic buffers grown by molecular beam epitaxy on (100) InP substrates, " J. Appl. Phys. 95, pp. 3952-3960 (2004).

  • O.Kwon, M.M Jazwiecki, R.N. Sacks and S.A. Ringel, "High Performance, Metamorphic InGaAs Tunnel Diodes Grown by Molecular Beam Epitaxy," accepted and to appear, IEEE Electron Dev. Lett. 24, pp. 613-615 (2003).

  • A. Armstrong, A. Arehart, B. Moran, S.P. DenBaars, U.K. Mishra, J. Speck and S.A. Ringel, "Impact of carbon on trap states in n-type GaN grown by metalorganic chemical vapor dposition," accepted and ot appear, Appl. Phys. Lett. (2003).

  • M.K. Hudait, Y. Lin, M.N. Palmisiano and S.A. Ringel, "0.6 eV bandgap In0.69Ga0.31As thermophotovoltaic devices grown on InAsP ste-graded buffers by molecular beam epitaxy," IEEE Electron Dev. Lett. 24, pp. 538-540

  • C.L. Andre, J.J. Boeckl, C.W. Leitz, M.T. Currie, T.A. Langdo, E.A. Fitzgerald and S.A. Ringel, "Low-temperature GaAs films grown on Ge and Ge/SiGe/Si substrates," J. Appl. Phys. 94, pp. 4980-4985 (2003).

  • M.K. Hudait, Y. Lin, D.M. Wilt, F. Wu, J.S. Spec, C.A. Tivarus, E.R. Heller, J.P. Pelz, and S.A. Ringel, "High Quality InAsP Step-Graded Buffer by Molecular Beam Epitaxy," Appl. Phys. Lett. Vol. 82, pp. 3212-3214 (2003).

  • A. Hierro, A.R. Arehart, B. Hieying, M. Hansen, U.K. Mishra, S.P. DenBaars, J.S. Speck, S.A. Ringel, "Impact of Ga/N Flux Ration on Trap States in n-Gan Grown by Plasma-Assisted Molecular-Beam Epitaxy," Applied Physics Letters, vol. 80, num. 5, pp. 805-807, 2002.

  • S.A. Ringel, J.A. Carlin, C.L. Andre, M.K. Hudait, M. Gonzalez, D.M. Wilt, E.B. Clark, P. Jenkins, D. Scheiman, A. Allerman, E.A. Fitzgerald, and C.W. Leitz, "Single Junction InGaP/GaAs Solar Cells Grown on Si Substrates with SiGe Buffer Layers," (Invited) Progress in Photovoltaics:  Research and Applicatoins Vol 10, pp. 417-426 (2002).

  • R.J. Kaplar, S.A. Ringel, Steven R. Kurtz, J.F. Klem, and A.A. Allerman, "Deep-Level Defects in InGaAsN Grown by Molecular-Beam Epitaxy," Applied Physics Letters, vol. 80, num. 22, pp. 1-4, Jun. 2002.

  • M.K. Hudait, C.L. Andre, O.Kwon, M.N. Palmisiano and S.A. Ringel, "High-Performance In0.53Ga0.47As Thermophotovoltaic Devices Grown by Solid Source Molecular Beam Epitaxy," IEEE Electron Device Letters Vol. 23, pp. 825-827, 2002.

  • R.J. Kaplar, A.R. Arehart, S.A. Ringel, A.A. Allerman, R.M. Sieg, and Steven R. Kurtz, "Deep Levels and Their Impact on Generation Current in Sn-doped InGaAsN," Journal of Applied Physics vol. 90, pp. 3405-3408, Oct. 2001.

  • R.J. Kaplar, D. Kwon, S.A. Ringel, A.A. Allerman, S.R. Kurtz, E.D. Jones "Deep Levels in P and N-type InGaAsN for high efficiency multi-junction III-V cells," Solar Energy Materials and Solar Cells vol. 66, pp.85-91, 2001.

  • J.A. Carlin, S.A. Ringel, E.A. Fitzgerald, and M. Bulsara, "High Lifetime GaAs on Si using GeSi Buffers and its Potential for Space Applications," Solar Energy Materals and Solar Cells vol.66, pp. 621-630, 2001.

  • A. Hierro, A. Arehart, B. Heying, M. Hansen, J.J. Boeckl, L. Zhao, J.S. Speck, U.K. Mishra, S.P. DenBaars, and S.A. Ringel, "Carrier Trapping and Recombination at Point Defects and Dislocations in MOCVD n-GaN," Physica Status Solidi vol. 228, pp. 937-946, 2001.

  • A. Hierro, A. Arehart, B. Heying, M. Hansen, J.S. Speck, U.K. Mishra, S.P. DenBaars, and S.A. Ringel, "Capture Kinetics of Electron Traps in MBE-Grown n-GaN," Physica Status Solidi vol. 228, pp. 309-313, 2001.

  • R.J. Kaplar, A.R. Arehart, S.A. Ringel, A.A. Allerman, R.M. Sieg, and S.R. Kurtz, "Deep Levels and Their Impact on Generation Current in Sn-Doped InGaAsN," Journal of Applied Physics vol.90, pp. 3405-3408, 2001

  • R.J. Kaplar, A.R. Arehart, S.A. Ringel, A.A. Allerman, R.M. Sieg and S.R. Kurtz, "Deep Levels in p and n-type InGaAsN for High Efficiency Multi-Junction III-V Cells," Solar Energy Materials and Solar Cells Vol. 69, pp. 85-91, 2001. 

  • J.A. Carlin, S.A. Ringel, E.A. Fitzgerald, M. Bulsara, "High Quality GaAs Growth by MBE on Si using GeSi Buffers and Prospects for Space Photovoltaics," Progress in Photovolaics: Research and Applications, vol. 8, pp 323-332, 2000.

  • A. Hierro, D. Kown, S.A. Ringel, M. Hansen, J.S. Speck, U.K. Mishra, and S.P. DenBaars, "Optically and Thermally Detected Deep Levels in n-type Shcottky and p+-n GaN diodes," Applied Physics Letters, vol. 76, num. 21, pp. 3064-3066, May 2000.

  • A. Hierro, S.A. Ringel, M. Hansen, J.S. Speck, U.K. Mishra, and S.P. DenBaars, "Hydrogen Passivation on Deep Levels in n-GaN," Applied Physics Letters, vol. 77, num. 10, pp. 1499-1501, Sept. 2000.

  • A. Hierro, D. Kwon, S.A. Ringel, S. Rubini, E. Pelucchi, and A. Francios, "Photocapacitance Study of Bulk Deep Levels in ZnSe Grown by Molecular-Beam Epitaxy," Journal of Applied Physics, vol. 87, num. 2, pp. 1-9, Jan. 2000.

  • J.A. Carlin, S.A. Ringel, E.A. Fitzgerald, M. Bulsara, B.M. Keyes, "Impact of GaAs Buffer Thickness on Electronic Quality of GaAs Grown on Graded Ge/GeSi/Si substrates," Applied Physics Letters, vol 76, num. 14, pp. 1884-1886, April 2000.

  • A. Hierro, S.A. Ringel, M.A. Hansen, U. Mishra, S. Denbaars, and J. Speck, "Optically and Thermally Detected Deep Levels in n-type GaN," Applied Physics Letters Vol. 76, pp. 3064-3066, 2000.

  • J.A. Carlin, S.A. Ringel, E.A. Fitzgerald and M. Bulsara, "High Quality GaAs Growth by MBE on Si Using GeSi Buffers and Prospects for SPace Photovoltaics," (Invited), Progress in Photovoltaics:  Research and Applications Vol. 8, pp. 323-332, 2000.

  • J.A. Carlin, S.A. Ringel, J.J. Boeckl, R.J. Kaplar and E.A. Fitzgerald, "High Lifetime GaAs on Si Using GeSi Buffers and its Potential for Space Applications," Solar Energy Materials and Solar Cells Vol. 66, pp. 621-630, 2000.

  • A. Hierro, D. Kwon, S.A. Ringel (45%), M. Hansen, U.K. Mishra, S.P. Denbaars and J.S. Speck, "Deep Levels in n-type Schottky and p+n Homojunction and GaN Diodes,"  Internet Journal of Nitride Research Vol. 5s1, pp. 1884-1886, 2000.

  • D. Kwon, R.J. Kaplar, S.A. Ringel, A.A. Allerman, Steven R. Kurtz and E.D. Jones, "Deep Levels in P-Type InGaAsN Lattice-Matched to GaAs," submitted, Appl. Phys. Lett., 1999.

  • Q. Xu, J.W.P. Hsu, J.A. Carlin, R.M. Sieg, J.J. Boeckl and S.A. Ringel, "Topographic and Electronic Studies of Wedge-Shape Surface Defects on AlGaAs/GaAs films grown on Ge Substrates," Applied Physics Letters Vol. 75. pp. 2111-2113, 1999.

  • A. Hierro, D. Kwo, L.J. Brillson, S.A. Ringel, S. Rubini, E. Pelucchi, and A. Franciosi, "Evidence for a Dominant Midgap Trap in n-ZnSe Grown by Molecular Beam Epitaxy," Applied Physics Letters Vol 75, pp. 832-834, 1999.

  • R.N. Sacks, L. Qin, M. Jazwiecki, S.A. Ringel, M.B. Clevenger, D. Wilt and M.S. Goorsky, "Growth and Characterization of Epitaxial FeAl/InAlAs/InP and III-V/FeAl/InAlAs/InP Structures," Journal of Vacuum Science and Technology Vol. B17, pp. 1289-1293, 1999.

  • R.M. Sieg, J.A. Carlin, J.J. Boeckl, S.A. Ringel, M.T. Currie, S.M. Ting, T.A. Langdo, G. Taraschi, E.A. Fitzgerald and B.M. Keyes, "High Minority-Carrier Lifetimes in GaAs Grown on Low-Defect-Density Ge/GeSi/Si Substrates," Appl. Phys. Lett. 73, 3111-3113, 1998.

  • Q. Xu, J.W.P. Hsu, S.M. Ting, E.A. Fitzgerald, R.M. Sieg and S.A. Ringel, "Scanning Force Microscopy Study of GaAs Films Grown on Offcut Ge Substrates," J. Electron. Mat., 1010-1016, 1998.

  • S.M. Ting, E.A. Fitzgerald, R.M. Sieg and S.A. Ringel, "Range of Defect Morphologies on GaAs Grown on Offcut (001) Ge Substrates, J. Electron Mat., 27, 451-461, 1998.

  • R.M. Sieg, S.A. Ringel, S.M. Ting and E.A. Fitzgerald, and R.N. Sacks, "Anti-Phase Domain-Free Growth of GaAs on offcut (001) Ge Substrates by Molecular Beam Epitaxy With Suppressed Ge Outdiffusion," J. Electron. Mat. 27, 900-907, 1998.

  • B.L. Anderson, L.J. Pelz, S.A. Ringel, B.D. Clymer and S.A. Collins, Jr., "Photonics Laboratory with Emphasis on Technical Diversity," IEEE Trans. Education 41, 194-202, 1998.

  • J.A. Carlin, S.A. Ringel, R.N. Sacks, and K.S. Yap, "Role of Al Content on Surface Structure Evolution of Low Temperature AlGaAs and its Effect on Critical Thickness," J. Vac. Sci. Tech. B16, 1998.

  • R.M. Sieg, S.A. Ringel, S.M. Ting, S.B. Samavedam, M. Currie, T. Landgo and E.A. Fitzgerald, "Toward Device-Quality GaAs Growth on Offcut Ge/GeSi/Si Substrates," J. Vac. Sci. Tech. B16, 1471-1474, 1998.

  • S.A. Ringel and B. Chatterjee, "Electrical Deactivation of Interstitial Zn in Heteroepitaxial InP by Hydrogen and its effect on Electronic Properties," J. Appl. Phys. 83, 5904-5912, 1998.

  • S.A. Ringel and B. Chatterjee, "Hydrogen Passivation of Interstitial Zn Defects in Heteroepitaxial InP Cell Structures and Influence on Device Characteristics, Progress in Photovoltaics: Research & Applications (Elsevier) 5, 423-431, 1997.

  • S.A. Ringel, "Hydrogen-Extended Defect Interactions in Lattice-Mismatched, Relaxed InP Heteroepitaxial Layers," Review Article, Solid State Electronics, vol. 41, pp. 359-380, 1997.

  • R.M. Sieg, R.N. Sacks and S.A. Ringel, "Application of Pyrometric Interferometry to the In-Situ Monitoring of InAlAs, InGaAs and Quaternary Alloy Growth on InP Substrates, " J. Crys. Growth vol. 175/176, pp. 256-261, 1997.

  • R.W. Hoffman, N.S. Faemi, V.G. Weizer, P.P. Jenkins, S.A. Ringel (20%), D.A. Scheiman, D.M. Wilt and D.J. Brinker, "High Beinning of LIfe Efficiency p/n InP Solar Cells,"  Progress in Photovoltaics, Vol. 5, pp. 158-163, 1997.

  • P.N. Grillot and S.A. Ringel, "Identification of Compositionally-Invariant Deep Levels Introduced by Plastic Strain in Epitaxial GeSi and Deformed Bulk Si," Appl. Phys. Lett., vol. 69, pp. 2110-2112, 1996.

  • R.M. Sieg, R.N. Sacks, P.N. Grillot and S.A. Ringel, "Improved Substrate Temperature Stability During MBE Growth Using Indium-Free Mounting of Small Substrates of Various Shapes," J. Vac. Sci. Tech. A, vol. 14, pp. 3283-3287,1 996.

  • P.N. Grillot, S.A. Ringel and E.A. Fitzgerald, "Structural, Electronic, and Luminescence Investigation of Strain-Relaxation Induced Electrical Conductivity Type Conversion in GeSi/Si Heterostructures," J. Appl. Phys. vol. 80, pp. 2823-2832, 1996.

  • B. Chatterjee and S.A. Ringel, "Effect of Extended Defects on the Formation and Dissociation Kinetics of Zn-H Complexes in Heteroepitaxial p-type InP Layers, Appl. Phys. Lett., vol. 69, pp. 839-841, 1996.

  • R.M. Sieg and S.A. Ringel ,"Re-Absorption, Bandgap Narrowing, and the Reconciliation of Photoluminescence Spectra with Electrical Measurements for n-type Indium Phosphide," J. Appl. Phys. vol. 80, pp. 448-458, 1996.

  • P.N. Grillot, S.A. Ringel and E.A. Fitzgerald, "Effect of Composition on Deep Levels in GexSi1-x Heteroepitaxial Layers and Evidence for Dominant Intrinsic Recombination-Generation in Relaxed Ge Layers on Si," J. Electron. Mat. vol. 25, pp. 1028-1036, 1996.

  • R.N. Sacks, R.M. Sieg and S.A. Ringel, "Investigation of the Accuracy of Pyrometric Interferometry in Determining AlxGa1-x As Growth Rates and Compositions," J. Vac. Sci. Tech. B. vol. 14, pp. 2157-2162, 1996.

  • B. Chatterjee, S.A. Ringel and R. Hoffman, Jr., "Hydrogen Passivation of n+p and p+n Heteroepitaxial InP Solar Cell Structures," Progress in Photovoltaics: Res. and Appl., vol. 4, pp. 91-100, 1996.

  • R.M. Sieg, B. Chatterjee and S.A. Ringel, "Evidence for Enhanced Zinc Interstitial Concentration in Strain-Relaxed Heteroepitaxial InP," Appl. Phys. Lett., vol. 66, pp. 3108-3110, 1995.

  • R.A. Mena, S.E. Schacham, E.J. Haugland, S.A. Alterovitz, P.G. Young, S.B. Bibyk and S.A. Ringel, "Characterization of the Transport Properties of Channel Delta-Doped Structures by Light-Modulated Shubnikov-de Haas Measurements," J. Appl. Phys., vol. 78, pp. 6626-6632, 1995.

  • R.A. Mena, S.E. Schacham, E.J. Haugland, S.A. Alterovitz, S.B. Bibyk and S.A. Ringel, "Subband Quantum Scattering Times for AlGaAs/GaAs Obtained Using Digital Filtering," J. Appl. Phys., vol. 78, pp. 3940-3944, 1995.

  • B. Chatterjee and S.A. Ringel, "Hydrogen Passivation and its Effects on Carrier Trapping by Dislocations in InP/GaAs Heterostructures," J. Appl. Phys., vol. 77, pp. 3885-3898, 1995.

  • P.N. Grillot, S.A. Ringel, E.A. Fitzgerald, G.P. Watson, "Electron Trapping Kinetics at Dislocations in Relaxed Ge.3 .Si.7 /Si Heterostructures," J. Appl. Phys., pp. 3248-3256, 1995.

  • P.N. Grillot, S.A. Ringel, E.A. Fitzgerald, G.P. Watson and Y.H. Xie, "Minority and Majority Carrier Trapping in Strain-Relaxed Ge0.3Si0.7/Si Heterostructure Diodes Grown by Rapid Thermal Chemical Vapor Deposition," J. Appl. Phys., vol. 77, pp. 676-685, 1995.

  • B. Chatterjee, S.A. Ringel, Sieg, R. Hoffman and I. Weinberg, "Hydrogen Passivation of Dislocations in InP on GaAs Heterostructures," Appl. Phys. Lett., vol. 65, pp. 58-60, 1994.

  • S.A. Ringel, A.W. Smith, M.H. MacDougal and A. Rohatgi, "Effects of CdCl2 on Electronic Properties of Molecular Beam Epitaxially-Grown CdTe/CdS Heterojunction Solar Cells, "J. Appl. Phys., vol. 70, no. 2, pp. 881-889, 1991.

  • S.A. Ringel and A. Rohatgi, "The Effects of Trap-Induced Lifetime Variations on the Design and Performance of High Efficiency GaAs Solar Cells," IEEE Trans. El. Dev., vol. 38, no. 11, pp. 2402-2409, 1991.

  • A. Rohatgi, R. Sudharsanan, S.A. Ringel, and M.H. MacDougal, "Growth and Process Optimization of Polycrystalline CdTe and CdZnTe Films for High Efficiency Solar Cells," Solar Cells, vol. 30, pp. 109-122, 1991.

  • S.A. Ringel, R. Sudharsanan, A. Rohatgi, M.S. Owens, and H.P. Gillis, "Effects of Annealing and Surface Preparation on the Properties of MBE-Grown Polycrystalline CdZnTe Films," J. Vac. Sci. Tech. A, vol. 8, no. 3, pp. 2012-2019, May/June 1990.

  • S.A. Ringel, R. Sudharsanan, A. Rohatgi, and W.B. Carter, "A Study of Cd(Zn,Mn)Te/CdS Films and Interfaces," J. Electron. Mater., vol. 19, no. 3, pp. 259-263, 1990.

  • A. Rohatgi, S.A. Ringel, R. Sudharsanan, P.V. Meyers, C.H. Liu, and V. Ramanathan, "Investigation of Polycrystalline CdZnTe, CdMnTe, and CdTe Films for Photovoltaic Applications," Solar Cells, pp. 219-230, vol. 27, 1990.

  • S.A. Ringel, A. Rohatgi, and S.P. Tobin, " An Approach Toward 25% Efficient GaAs Heteroface Solar Cells," IEEE Trans. Electron. Dev., vol. 36. no. 7, pp. 1230-1237, 1989.

  • A.B. Dewald, R. L. Frost, S.A. Ringel, J.P. Schaffer, A. Rohatgi, B. Nielson, and K.G. Lynn, "Positron Annihilation Spectroscopy of AlGaAs/GaAs Interfaces in MOCVD-Grown GaAs Heterojunction Solar Cells," J. Vac. Sci. Technol., vol. A6, no. 4, pp. 2248-2252, 1988.

  • A. Rohatgi, S.A. Ringel, J. Welch, E. Meeks, K. Pollard, A. Erbil, C.J. Summers, P.V. Meyers, and C.H. Liu, "Growth and Characterization of CdMnTe and CdZnTe Polycrystalline Thin Films for Solar Cells," Solar Cells, vol.24, pp. 185-194, 1988.

  • S.A. Ringel and S. Ashok, "Silicon Surface Barrier Modification by Low Energy Nitrogen Ion Implantation, " J. Electrochem. Soc., vol. 134, no. 6, pp. 1494-1499, 1987.

  • S.A. Ringel, H.C. Chien, and S. Ashok, "Evidence for the Formation of Polycrystalline Silicon by Argon Implantation and its Passivation by Hydrogen," Appl. Phys. Lett., vol. 49, no. 12, pp. 728-730, 1986.

  • S.A. Ringel, X.C. Mu, S.J. Fonash, and S. Ashok, "A Study of Target Heating in Low Energy Ion Beam Processing," J. Vac. Sci. Technol., vol. A4, no. 5, pp. 2385-2388, 1986.

  • S. Ashok and S.A. Ringel, "Low-Energy Hydrogen Implantation for Silicon Schottky Barrier Modification," Vacuum, vol. 36, no. 11, pp. 917-920, 1986.

  • K. Giewont, S.A. Ringel, and S. Ashok, "Synergistic Effects in Ion Bombardment Modification of Silicon Schottky Contacts," J. Vac. Sci. Technol. A , vol. 4, no. 3, pp. 845-846, 1986.


INVITED PRESENTATIONS and SEMINARS

  • S.A. Ringel, "Quantitative Trap Spectroscopy in Wide Bandgap Semiconductors, Interlayers," Int. Conf. On Defects in Semiconductors ICDS-24, Albuquerque, NM, 2007. Tutorial.

  • S.A. Ringel, A. Armstrong, A. Chakraborty, S. Rajan, J.S. Speck, S.P. DenBaars, and U.K. Mishra, "High-Resolution Depth-Resolved Trap Spectroscopy of AlGaN Devices, Interlayers," WOCSDICE, Venice, Italy, 2007.

  • M. Gonzalez, A. Carlin, R.J. Walters, S.R. Messenger, J.H. Warner, J.R. Lorentzen, C. Dohrman, E.A. Fitzgerald, and S.A. Ringel, "Radiation Response and Induced Traps in InGaP/GaAs Multijunction Materials and Cells Grown on Metamorphic Si-based Substrates, Interlayers," 20th Space Photovoltaic Research and Technology Conf., Cleveland, 2007.

  • S.A. Ringel, A. Armstrong, A. Malonis, A. Chakrobart, S. Rajan, S.P. DenBaars, J.S. Speck, and U.K. Mishra, "Trap Spectroscopy of AlGaN/GaN HEMT Structures, Interlayers," DoD Tri-Services Reliability Workshop, Adelphi, MD, 2007.

  • S.A. Ringel, "Nanostructured materials and photovoltaics: Opportunities and Challenges, Interlayers," 4th Ohio Nanotechnology Summit, Akron, OH, 2007 Plenary.

  • S.A. Ringel, A. Armstrong, C. Poblenz, S. Rajan, U.K. Misha, and J.S Speck, "Depth-resolves trap spectroscopy of AlGaN/GaN devices, Interlayers," WOCSEMMAD, Savannah, GA, 2007.

  • J.A. Carlin, C.L. Andre, O. Kwon, M. Gonzalez,M. Lueck, E.A. Fitzgerald, D. Wilt, and S.A. Ringel, "III-V device integration on Si metamorphic SiGe substrates, Interlayers," Electrochemical Society, Cancun, 2006.

  • S.A. Ringel, "Metamorphic III-V/Si photovoltaics for terrestrial and space power, Interlayers," Key Conference 2006, San Antonio, 2006.

  • S.A. Ringel, "The science and application of metamorphic semiconductor heterostructures: a new age of advanced device technology reaches puberty, Interlayers," University of Notre Dame ECE Colloquium, South Bend, IN, 2006.

  • S.A. Ringel, O. Kwon, M. Luek, J. Boeckl, and E.A. Fitzgerald, "III-V/Si device integration via metamorphic SiGe substrates, Interlayers," 3rd International SiGe Technology and Device Meeting, Princeton, NJ, 2006.

  • A. Armstrong, S.A. Ringel, C. Poblenz, S. Rajan, U.K. Misha, and J.S. Speck, "Observation of AlGaN related deep levels in AlGaN/GaN heterostructures, Interlayers," WOCSEMMAD, Tempe, AZ, 2006.

  • S.A. Ringel, "Control of mismatched interfaces and defects in III-V heteroepitaxy, Interlayers," Intel Corporation, Hillsboro, OR, 2006.

  • S.A. Ringel, "Defect Engineering in III-V/Si Integration and Applications fro Optoelectronics and Photovoltaics Interlayers," International Conference of Materials for Advanced Technologies (ICMAT), Singapore, 2005.

  • S.A. Ringel, "Nanomaterials in Emerging Semiconductor Device Technologies (ICMAT) Interlayers," Nano-Applications Summit, Cleveland, OH, 2005.

  • S.A. Ringel, "Heterogeneous Integration for High Performance, Low-Cost Solar Cells, Interlayers," Shanghai Jiao Tong University, College of Engineering Colloquium, Shanghai, China 2005.

  • S.A. Ringel, "Defect Engineering and Characterization in Lattice-Mismatched Semiconductor Heterostructures: Wide Bandgap Electronics and Photovoltaics, Interlayers," Georgia Tech Electrical and Computer Engineering Colloquium, April 2005.

  • S.A. Ringel, "Detection, Analysis and Impact of Carbon-Related Bandgap States in MBE-Grown GaN:C, Interlayers," Northrop Grumman Science and Technology, Redondo Beach, CA, 2005.

  • S.A. Ringel, "Virtual InAs Interlayers," WOCSEMMAD, Miami, FL, 2005.

  • S.A. Ringel, "On the Controversy Regarding Carbon States and Luminescence in GaN, Interlayers," American Physical Society, Los Angeles, CA, 2005.

  • S.A. Ringel, C.L. Andre, M. Luek, D. Issacson, A.J. Pitera, E.A. Fitzerald, and D.M. Wilt, "III-V Multi-Junction Materials and Solar Cells on Engineered SiGe/Si Substrates, Interlayers," Mater. Res. Soc. Symp., Boston, MA, Proc. in print 2005.

  • S.A. Ringel, C.L. Andre, D.M. Wilt, and E.A. Fitzgerald, "Advances in III-V Solar Cells and Heterostructures on SiGe Substrates, Interlayers," Solar Electric Technology Review, Denver, CO, 2004.

  • S.A. Ringel, "Solar Energy Technology: Research, Development and Commercialization Interlayers," National University of Singapore and Massachusetts Institute of Technology Live Internet II international broadcast, Singapore-MIT Alliance (SMA), 2004.

  • S.A. Ringel, "Epitaxial Integration of III-V Materials with Metamorphic SiGe Substrates, Interlayers," (Invited) ONR Workshop on Frontiers in Epitaxy, Moab, UT, 2004.

  • S.A. Ringel, "Defect States in Carbon-Doped GaN Grown by MBE and MOCVD with varying Dislocation Density Interlayers," WOCSEMMAD, Pasadena, CA, 2004.

  • S.A. Ringel, "Deep Traps and Levels in GaN: Detection, Properties and the Dilemma of Identifying Device-Relevant Defect Properties, Interlayers," Institute for Materials Research, Singapore, 2004.

  • S.A. Ringel, "Deep Traps and Levels in GaN: Detection, Properties and the Dilemma of Identifying Device-Relevant Defect Properties, Interlayers," Nanyang Technological University, Singapore, 2004.

  • S.A. Ringel, "Deep Traps and Relation to Growth Conditions in GaN Grown by MOCVD and MBE Interlayers," WOCSEMMAD, Pasadena, CA, 2004.

  • S.A. Ringel, and C.L. Andre, D.M. Wilt, E.A. Fitzgerald, M. Lee, A. Pitera, M. Smith, D. Scheiman, and P. Jenkins, "Advances in p+n and n+p GaAs solar cells grown on SiGe/Si substrates, Interlayers," 18th Space Photovoltaic Research and Technology Conf., Cleveland, 2003.

  • S.A. Ringel, A. Armstrong, A. Arehart, B. Moran, Umesh K. Mishra, and J.S. Speck, "Detection of Carbon-Related Bandgap States in GaN Using Deep Level Optical Spectroscopy, Interlayers," International Symposium On Compound Semiconductors, San Diego, CA, 2003.

  • S.A. Ringel, "Characterization of Deep Level Defects in Wide Bandgap Nitrides Using Deep Level Optical Spectroscopy, Interlayers," ONR Workshop on Characterization Techniques in Wide Gap Semiconductors, Maui, HI, 2003.

  • S.A. Ringel, "Advances in III-V Compounds and Solar Cells on SiGe Substrates, Interlayers," National Center for Photovoltaics Review Meeting, Denver, CO, 2003.

  • S.A. Ringel, C.L. Andre, A. Khan, M. Gonzalez, M.K. Hudait, E.A. Fitzgerald, J.A. Carlin, M.T. Currie, C.W. Leitz, and T.A. Langdo, "Device-Quality III-V Compound Semiconductor Epitaxy on Si Via SiGe Interlayers, Interlayers," 49th American Vacuum Society International Symp., Denver, CO, 2002.

  • S.A. Ringel, A. Hierro, A. Arehart, J. Boeckl, B. Heying, M. Hansen, L. Zhai, J.S. Speck, U.K. Mishra, and S.P. DenBaars, "Deep Levels Associated with Extended Defects in MOCVD and MBE Grown n-GaN, Interlayers," ONR Wkshp. On Extended Defects in Wide Gap Semicon.: Elec. And Optical Effects, San Pedro, Belize, 2002.

  • S.A. Ringel, G.m. Serrer, and D.J. Flood, "Part I: The Center for Electronic Materials and Devices in Aerospace Power and Energy Conversion - CEECAP; Part II: Si-Based Substrate Engineering for Next Generation III-V Photovoltaics, Interlayers," Solar Cirlce Colloquium (NASA Glenn Res. Ctr, Cleveland), 2002.

  • S.A. Ringel, "Deep Traps and Relation to Growth Conditions in GaN Grown by MOCVD and MBE Interlayers," WOCSEMMAD 2002, Austin, TX, 2002.

  • S.A. Ringel, "Device-Qulaity GaAs and High Performance Minority Carrier GaAs Devices Grown on Si Using Graded SiGe Buffers, Interlayers," WOCSEMMAD 2002, Austin, TX, 2002.

  • S.A. Ringel, M.K. Hudait, and Y. Lin, "Themermophotovoltaic Materials and Devices Grown by Molecular Beam Epitaxy, Interlayers," Thermophotovoltaics Program Review, Pittsburgh, PA, 2002.

  • C.L. Andre, A. Khan, M. Gonzalez, M.K. Hudait, E.A. Fitzgerald, J.A. Carlin, M.T. Currie, C.W. Leitz, T.A. Langdo, E.B. Clark, D.M. Wilt, and S.A. Ringel, "Impact of Threading Disolocations on Both n/p and p/n Single Junction GaAs Cells Grown on Ge/SiGe/Si Substrates," 29th IEEE PVSC, New Orleans, 2002.

  • S.A. Ringel, J.A. Carlin, C.L. Andre, J. Boeckl, C.W. LeitzM. Currie, T. Langdo, E.A. Fitzgerald, A. Allerman, D.M. Wilt, and E.B. Clark, "Develpment of High Efficiency GaAs-onSi Solar Cells Using GeSi Interlayers," Space Power Workshop(Invited), Redondo Beach, CA, 2001.

  • O. Kwon and S.A. Ringel, "Growth and Properties of Lattice-Matched and Mismatched for mid-infrared Devices Grown on Graded InAlAs/InP Substrates InGaAs Tunnel Junctions," 43rd TMS Electronic Materials Conference, South Bend, IN, 2001.

  • S.A. Ringel, J.A. Carlin, C.L. Andre, A. Allerman, E. Clark, D.M. Wilt, C. Leitz, E.A. Fitzgerald, "Performance Advances of InGaP/GaAs Solar Cells on Si Using GeSi Buffers," Presented at Space Research and Technology XVII (SPRAT XVII) Conference, Cleveland, Oh, 2001.

  • A. Hierro, A.R. Arehart, S.A. Ringel, B. Heying, M. Hansen, J.S. Speck, U.K. Mishra, and S.P. DenBaars, "Impact of Ga/N Flux Ratio on the Deep Level Spectrum in MBE-grown n-GaN," 4th International Conference on Nitride Semiconductors (ICNS-4), July 2001 (Proc. in print).

  • S.A. Ringel, "Electron Traps in N-GaN," UCLA Electrical Engineering Colloqium, April 2001.

  • S.A. Ringel, J.A. Carlin, C.L. Andre, and J. Boeckl, "Development of High Efficiency GaAs-on-Si Solar Cells Using GeSi Interlayers," NASA Solar Cell/Array Tech Review, Cleveland, OH, April 2001.

  • S.A. Ringel, "Electron Traps in N-GaN," Amberwave Systems Corp, Salem, NH, April 2001.

  • S.A. Ringel, "III-V Compound Photovoltaics on Si Using GeSi-Based Virtual Substrates," National Renewable Energy Laboratory Program Review, Golden, CO, Oct. 2001.

  • S.A. Ringel, "Identification of Deep Traps and Their Sources in GaN," Air Force Research Laboratory, WPAFB, Dayton, OH Dec. 2001.

  • S.A. Ringel, M.K. Hudait, and Y. Lin, "Thermophotovoltaic Materials and Devices Grown my Molecular Beam Epitaxy," Direct Energy conversion Workshop, Washington DC, Dec. 2001.

  • S.A. Ringel, "Deep Levels in Nitrides," ONR-Center for Advanced Nitride Kickoff, Univ. Cal. Santa Barbara, May 2001.

  • S.A. Ringel, "Deep Level Defects in GaN: Electronic Properties and Toward Identification of Physical Sources," Sandia National Laboratories, Feb. 2001.

  • S.A. Ringel, "Electronic Deep Level Spectroscopy and Applications for infrared-Ultraviolet Optoelectronics and High Temperature Devices," Bechtel-Bettis Atomic Power Laboratory, West Mifflin, PA, Feb. 2001.

  • J.A. Carlin, M.K. Hudait, S.A. Ringel, D.M. Wilt, E.B. Clark, C.W. Leitz, M. Currie, T. Langdo, and E.A. Fitzgerald, "High Efficiency GaAs-on-Si Solar Cells with High Voc Using Graded GeSi Buffers," 28th IEEE PVSC-Anchorage, AK, September 2000.

  • S.A. Ringel, J.A. Carlin, R.M. Sieg, J.J. Boeckl, E.A. Fitzgerald, M. Bulsara, "Materials Issues for High-Efficiency, Lightweight III-V Space Solar Cells on Ge/GeSi/Si Substrates," Fall Materials Research Society Meeting, Boston, MA, Dec. 1, 1998 (proc. in print).

  • S.A. Ringel, R.M. Sieg and J.A. Carlin, "Highly-Controlled GaAs/Ge Interfaces and Implications for III-V Cells on Si," Space Power Workshop, Long Beach, CA, 1998.

  • S.A. Ringel, J.A. Carlin, R.M. Sieg, and E.A. Fitzgerald, "Highly-Controlled GaAs/Ge Interfaces and Implications for III-V Optoelectronic Integration onto Group IV Substrates," Engineering Foundation Conference on Lattice-Mismatched and Heterovalent Epitaxy, Barga, Italy, 1998 (proc. in print, AIP).

  • R. J. Kaplar, D. Kwon, and S. A. Ringel, A. A. Allerman, Steven R. Kurtz and H. Q. Hou,"Deep Level Defects in MOCVD-Grown InGaAsN Lattice-Matched to GaAs," 40th TMS/IEEE Electronic Materials Conference, Charlottesville, VA, 1998.

  • S.A. Ringel, R.M. Sieg, J.A. Carlin, S. Ting, M. Currie, V. Yang, E.A. Fitzgerald, M. Bulsara and B.M. Keyes, "Toward Achieving Efficient III-V Space Cells on Ge/GeSi/Si Wafers," Proc. 2nd World Conf. and Exhib. on Photovoltaic and Solar Energy Conversion, Vienna, Austria , proc. in print, 1998.

  • R.N. Sacks, L. Qin, M. Jazwiecki, S.A. Ringel, M.B. Clevenger, D.Wilt, and M.S. Goorsky, "Growth and characterization of epitaxial FexAl1-x/(In,Al)As/InP and III-V/ FexAl1-x/(In,Al)As/InP structures," 17th North American Conf. on Molecular Beam Epitaxy, State College, PA, 1998.

  • M.B. Clevenger, C.S. Murray, S.A. Ringel, R.N. Sacks, L. Qin, G.W. Charache and D.M. DePoy, "Optical Properties of Thin Semiconductor Device Structures with Reflective Back Surface Layers," 4th NREL Workshop on Thermophotovoltaics, Denver, CO, proc. in pring (AIP), 1998.

  • S.A. Ringel, R.N. Sacks, L. Qin, M.B. Clevenger and C.S. Murray, "Growth and Properties of InGaAs/FeAl/InAlAs/InP Heterostructures for Buried Reflector/Interconnect Applications in InGaAs Thermophotovoltaic Devices, 4th NREL Workshop on Thermophotovoltaics, Denver, CO, proc. in pring (AIP), 1998.

  • D. Kwon, R.J. Kaplar, S.A. Ringel, A.A. Allerman, S.R. Kurtz and E.D. Jones, "Deep Level Defect Studies in MOCVD-Grown InGaAsN Films Lattice-Matched to GaAs, Fall Materials Research Society Meeting, Boston, MA, 1998 (proc. in print).

  • A. Hierro, D. Kwon, S.A. Ringel, L.J. Brillson, J. Schaefer, A. P. Young and A. Franciosi, "Deep Level Characterization of interface-engineered ZnSe Layers on GaAs Grown by Molecular Beam Epitaxy," Fall 1998 Materials Research Society Meeting, Boston, MA, 1998 (proc. in print).

  • R.M. Sieg, S.A. Ringel, S.M. Ting, S.B. Samavedam, M. Currie, T. Langdo and E.A. Fitzgerald, "Toward Device-Quality GaAs Growth by MBE on Offcut Ge/Si1-xGex/Si Substrates," 16th North American Conf. On Molecular Beam Epitaxy, Ann Arbor, MI, 1997.

  • J.A. Carlin, S.A. Ringel and R.N. Sacks, "Role of Al Content on Surface Roughening and Critical Thickness of Low Temperature AlxGa1-xAs, " 16th North American Conf. On Molecular Beam Epitaxy, Ann Arbor, MI, 1997.

  • B. Chatterjee, S.A. Ringel and R.W. Hoffman, Jr., "Hydrogen-Interstitial Zn Defect Complexes and Their Interactions on the Device Characteristics of Heteroepitaxial p+n InP Cell Structures," Proc. 26th IEEE Photovoltaic Specialists Conf., pp. 907-910, Anaheim, CA, 1997.

  • S.A. Ringel, R.M. Sieg, S.M. Ting and E.A. Fitzgerald, "Anti-Phase Domain-Free GaAs on Ge Substrates Grown by Molecular Beam Epitaxy for Space Solar Cell Applications, " Area Plenary Presentation, Proc. 26th IEEE Photovoltaic Specialists Conf., Anaheim, CA, pp. 793-798, 1997.

  • R.W. Hoffman, Jr., N.S. Fatemi, P.P. Jenkins, V.G. Weizer, S.A.Ringel, D.A. Scheiman, D.M. Wilt and D.J. Brinker, "Improved Performance of p/n InP Solar Cells," Proc. 26th IEEE Photovoltaic Specialists Conf., pp. 815-818, Anaheim, CA, 1997.

  • R.M. Sieg, S.A. Ringel, S.M. Ting and E.A. Fitzgerald, "Device-Quality Gallium Arsenide Grown on Offcut Ge Substrates by Molecular Beam Epitaxy for Solar Cells," Fall MRS Meeting, Boston, MA, 1997.

  • R.W. Hoffman, Jr., N.S. Fatemi, V.G. Weizer, P. Jenkins, M.A. Stan, S.A.Ringel, R.M. Sieg, D.A. Scheiman, D.M. Wilt and D.J. Brinker, "The Effect the Zn Intersitital Defect on the Performance of p/n InP Solar Cells, " Proc. Fall MRS Meeting, pp. 235-240, Boston, MA, 1997.

  • B.Chatterjee and S.A. Ringel, "Properties of Hydrogen-Zn Interstitial Complexes in Heteroepitaxial InP and their Effect on Device Stability," 39th TMS/IEEE Electronic Materials Conference, Ft. Collins, CO,1997.

  • S.M. Ting, E.A. Fitzgerald, R.M. Sieg and S.A. Ringel, "Range of Defect Morphologies for GaAs Grown on Offcut Ge Substrates," 39th TMS/IEEE Electronic Materials Conference, Ft. Collins, CO,1997.

  • R.M. Sieg, S.A. Ringel, S.M. Ting and E.A. Fitzgerald, "Anti-Phase Domain-Free GaAs Grown on Ge Substrates by Molecular Beam Epitaxy Using Either As or Ga Terminated Ge Surfaces," 39th TMS/IEEE Electronic Materials Conference, Ft. Collins, CO,1997.

  • Q. Xu, J.W.P. Hsu, S.M. Ting, E.A. Fitzgerald, R.M. Sieg and S.A. Ringel, "Scanning Force Microscopy Study of GaAs Films Grown on Offcut Ge Substrates," 39th TMS/IEEE Electronic Materials Conference, Ft. Collins, CO,1997.

  • S.A. Ringel and B. Chatterjee, "Hydrogen Passivation of Interstitial Zn Defects in Heteroepitaxial InP Cell Structures and Influence on Device Characteristics," Proc. Space Photovoltaics Research and Technology Conference XV, Cleveland, OH, 1997.

  • S.A. Ringel, "Dislocation Interactions and Their Impact on Electrical Properties of GeSi-based Heterostructures," Materials Research Society Symp. Proc. vol. 442, pp. 313-324, Boston, MA, 1996.

  • R.W. Hoffman, N.S. Faemi, V.G. Weizer, P.P. Jenkins, S.A. Ringel, D.A. Scheiman, D.M. Wilt and D.J. Brinker, "High Beginning of Life Efficiency p/n InP Solar Cells," Proc. Space Photovoltaics Research and Technology Conference XV, Cleveland, OH, 1997.

  • R.M. Sieg, R.N. Sacks and S.A. Ringel, "Application of Pyrometric Interferometry to the In-Situ Monitoring of In(AlGa)As Growth on InP Substrates," 16th North American Molecular Beam Epitaxy Conf., Malibu, CA, 1996.

  • B. Chatterjee and S.A. Ringel, "Dissociation Kinetics and Properties of Hydrogen-Extended Defect Complexes in Lattice-Mismatched InP Heteroepitaxial Layers," 38th TMS/IEEE Electronic Materials Conference, Santa Barbara, CA,1996. Abstract published, J. Electronic Mat. vol. 25, p. A41, 1996.

  • P.N. Grillot, S.A. Ringel, E.A. Fitzgerald and J. Michel, "Dislocation Interaction and Doping Compensation in Compositionally Graded GexSi1-x/Si Heterostructures," 38th TMS/IEEE Electronic Materials Conference, Santa Barbara, CA,1996. Abstract published, J. Electronic Mat. vol. 25, p. A57, 1996.

  • B. Chatterjee, S.A. Ringel and R. Hoffman, "A Comparison of Hydrogen Passivation in Heteroepitaxial n+p and p+n InP Solar Cells," Proc. 25th IEEE Photovolt. Spec. Conf., proc., pp. 179-182, Washingtion, DC, 1996.

  • R.W. Hoffman Jr., N. S. Fatemi, P.P. Jenknis, D.A. Scheiman, S.A. Ringel, W. Davis, V.G. Weizer, D.M. Wilt and D.J. Brinker, "Development of High Efficiency p+/n InP Solar Cells for Heteroepitaxial Applications," Proc. 25th IEEE Photovolt. Spec. Conf., proc., pp. 171-174, Washingtion, DC, 1996.

  • P.N. Grillot, S.A. Ringel, E.A. Fitzgerald and J. Michel, "Electrical Conductivity Type Conversion Due to Strain-Relaxation Related Defects in GexSi1-x/Si," 1996 Spring Materials Research Society Meeting, San Francisco, 1996.

  • B. Chatterjee, W.C. Davis, S.A. Ringel and R. Hoffman, Jr, "Hydrogen Passivation of n+p and p+n Heteroepitaxial InP Solar Cell Structures," Proc. Space Photovoltaics Research and Technology Conference XIV, Cleveland, OH, pp. 127-136, 1995.

  • R.N. Sacks, R.M. Sieg and S.A. Ringel, "Investigation of the Accuracy of Pyrometric Interferometry in Determining AlxGa1-x As Growth Rates and Compositions," 15th North American Molecular Beam Epitaxy Conf., College Park, MD, 1995.

  • P.N. Grillot, S.A. Ringel, E.A. Fitzgerald and T.W Sorsch, "Effect of Composition on Traps and Recombination-Generation Centers in GexSi1-x Epitaxial Layers Graded to Pure Ge," 37th TMS/IEEE Electronic Materials Conf., Charlottesville, VA, 1995. Abstract published, J. Electronic Mat. vol. 24, pp. A7-A8, 1995.

  • P.N. Grillot, S.A. Ringel, E.A. Fitzgerald, G.P. Watson, J.L. Benton and Y.H. Xie, "Dislocation Related Carrier Trapping in Relaxed, Compositionally Graded GeSi/Si Grown by Chemical Vapor Deposition," 36th TMS/IEEE Electronic Materials Conference, Boulder, CO., 1994. Abstract published, J. Electronic Mat. vol. 23, pp. A13, 1994.

  • S.A. Ringel and B. Chatterjee, "Material Quality and Dislocation Trapping in Hydrogen-Passivated Heteroepitaxial InP/Ge and InP/GaAs Solar Cells," Proc. 1st IEEE World Conf. on Photovoltaic Energy Conversion, Waikoloa, Hawaii, pp. 2204-2208, 1994.

  • S.A. Ringel and B. Chatterjee, "Effects of Plasma Hydrogenation on Trapping Properties of Dislocations in Heteroepitaxial InP/GaAs," Proc. Space Photovoltaics Research and Technology Conference XIII, Cleveland, OH, pp. 401-408, 1994.

  • P.N. Grillot, S.A. Ringel, E.A. Fitzgerald, G.P. Watson, J.L. Benton and Y.H. Xie, "Dislocation Related Carrier Trapping in Relaxed, Compositionally Graded GeSi/Si Grown by Chemical Vapor Deposition," Presented at TMS Electronic Materials Conference, Boulder, CO., June 21-23, 1994.

  • P.N. Grillot, S.A. Ringel, G.P. Watson, E.A. Fitzgerald and Y.H. Xie, "Electronic Characterization of Dislocations in RTCVD Germanium-Silicon /Silicon Grown by Graded Layer Epitaxy," Materials Research Society Symp. Proc. vol. 325, pp. 159-164, Boston, MA, 1994.

  • B. Chatterjee, S.A. Ringel, R. Sieg, I. Weinberg and R. Hoffman, "Deep Level Characterization and Passivation in Heteroepitaxial InP," Materials Research Society Symp. Proc. vol. 325, pp. 125-130, Boston, MA, 1994.

  • B. Chatterjee, R. Sieg, S.A. Ringel, R. Hoffman and I. Weinberg, " Identification and Passivation of Mismatch Related Deep Levels in Heteroepitaxial InP on GaAs Substrates," Joint Proc. of Symp. On Long Wavelength Infrared Detectors and State of the Art Program on Compound Semiconductors, 184th Meeting of the Electrochemical Society, in press, 1994, New Orleans; extended abstract published in The Electrochemical Society Interface, vol. 2, no. 3, pp. 149-150, 1993.

  • A. Rohatgi, S.A. Ringel, R. Sudharsanan and H.C. Chou, An Improved Understanding of Efficiency Limiting Defects in Polycrystalline CdTe/CdS Solar Cells, Proc. twenty second IEEE Photovoltaic Specialists Conf, pp. 962-966, 1991.

  • S.A. Ringel, R. Sudharsanan, A. Rohatgi, M.S. Owens, and H.P. Gillis, "Effects of Annealing and Surface Preparation on the Properties of MBE-Grown CdZnTe Films," presented at the 36th American Vacuum Society National Symposium, Boston, MA, 1989.

  • S.A. Ringel and A. Rohatgi, "Material Quality and Design Optimization for High Efficiency aAs Solar Cells," Proc. of the Twentieth IEEE Photovoltaic Specialists' Conf., Las Vegas, pp. 666-671, 1988.

  • A. Rohatgi, R. Sudharsanan, S.A. Ringel, P.V. Meyers, and C.H. Liu, "Wide Bandgap thin Film Solar Cells From CdTe Alloys," Proc. of the Twentieth IEEE Photovoltaic Specialists' Conf, Las Vegas, pp. 1477-1481, 1988.

  • A.B. Dewald, R.L. Frost, S.A. Ringel, J.P. Schaffer, A. Rohatgi, B. Nielson, and K.G. Lynn, "Positron Annihilation Spectroscopy of AlGaAs/GaAs Interfaces in MOCVD-Grown GaAs Heterojunction Solar Cells," 34th American Vacuum Society National Symposium, Anaheim, CA, 1987.

  • S. Ashok and S.A. Ringel, "Silicon Surface Modification by Low Energy Ion Implantation," First International Conf. on Semiconductor and Integrated Circuit Technology," Beijing, China, 1986.

  • S. Ashok and S.A. Ringel, "Low-Energy Hydrogen Implantation for Silicon Schottky Barrier Modification," 4th Low Energy Ion Beams Conf., Brighton, U.K., 1986.

  • S.A. Ringel and S. Ashok, "Silicon Surface Barrier Modification by Low Energy Nitrogen Ion Implantation," 167th Meeting of the Electrochemical Society, Toronto, Canada, 1985.