Charles H. Knapp Endowed Chair
Phone: (860) 486-9425
ali.gokirmak (at) uconn.edu
- Ph.D. Electrical & Computer Engineering, Cornell University, 2005
- M.S. Electrical & Computer Engineering, Cornell University, 2002
- B.S. Physics, University of Maryland at College Park, 1998
- B.S. Electrical Engineering, University of Maryland at College Park, 1998
- Phase change memory (PCM)
- Thermoelectric effects
- Phase change logic
- Current induced crystallization
- Applications of nanostructures
- Nanofabrication technologies
- Small-scale MOSFET’s for sensors, logic and non-volatile memories
- Electrical characterization
- Finite element modeling
Federal Research Grants (Share: $3M, Leading: $2.8M, Total involved: $11.2M, UConn Nanoelectronics Laboratory total: $5.1M)
- DURIP (Defense University Research Instrumentation Program): #FA9550-18-1-0290 “Physical vapor deposition system,” Ali Gokirmak, Helena Silva ($471,500, 50%), 8/13/2018-8/12/2020.
- NSF ECCS 1711626: “Integration of Phase Change Devices with Silicon Electronics for Increased Functionality and Performance,” Ali Gokirmak, ($471,999, 100%), 7/1/2017 ~ 12/30/2022.
- AFOSR (Air Force Office of Scientific Research) FA9550-14-1-0351Z MURI: “Development of Universal Security for evaluation and design of nanoscale devices,” Tehranipoor, M. Van Dijk, A. Gokirmak, H. Silva, D. Forte, J. Shi, G. Qu, A. Srivastava, F. Koushanfar ($7,400,000, 10%), 11/2014-12/2020.
- DOE BES (Dept. of Energy, Basic Energy Sciences): “Crystallization and thermoelectric transport in semiconductor nanostructures,” Gokirmak, H. Silva ($450,000, 50%), 9/1/2013-8/31/2016.
- NSF ECCS 1150960: “CAREER: Phase-change memories and electro-thermal effects at nanoscale,” A. Gokirmak ($532,800, 100%), 2/1/2012-7/31/2018.
- DOE BES (Dept. of Energy, Office of Basic Energy Sciences): “Crystallization and thermoelectric transport in silicon nanostructures,” Gokirmak, H. Silva ($512,000, 50%), 9/1/2010-8/31/2013.
- NSF ECCS 0824171: “GOALI: Side gated ultra narrow channel silicon MOSFETs and transport studies at nanometer scale,” Gokirmak and R. Nunes, ($307,075 100%), 8/1/2008-7/31/2013.
- NSF CCMI 0730826 “EXP-LA: Real-time, compact, and ultra sensitive sensor arrays for explosives vapor detection,” Y.Lei, Y. Yan, C. Brueckner, A. Gokirmak ($792,404, ~5%), 9/1/2007-8/1/2010.
- NSF ECCS 0702307 “Tunable Photonic Nanostructures Exhibiting Plasmonic and Leaky-mode Resonances,” R. Magnusson, A. Gokirmak ($300,000, 50%), 5/23/2007-5/22/2010.
- 2019-2020 Electrical & Computer Engineering Outstanding Teaching Award, University of Connecticut
- 2020 Charles H. Knapp Endowed Professorship
- 2012 NSF CAREER Award
- Spring 2009 Dean of Engineering recognition for outstanding teaching, University of Connecticut
- 2008-2009 Electrical & Computer Engineering Outstanding Teaching Award, University of Connecticut
- 2000-2003 IBM Ph.D. Fellowship
- 1997-1998 Roberta Ma Scholarship, University of Maryland College Park
PhD Thesis Supervised at UConn
- Gokhan Bakan “Thermoelectric Effects in Self-heating Silicon Microwires,” 1/2013 (Major Co-Advisor)
- Faruk Dirisaglik “High-Temperature Electrical Characterization of Ge2Sb2Te5 Phase Change Memory Devices,” 10/2014 (Advisor)
- Mustafa Akbulut, “Narrow Channel Accumulated Body MOSFETs: Design, Modeling and Experimental Verification,” 8/2015 (Major Co-Advisor)
- Adam Cywar, “Melting and Crystallization of Si and Ge2Sb2Te5 Nanostructures,” 1/2016 (Advisor)
- Nadim Kan’an, “Phase Change Devices for Nonvolatile Logic,” 5/2017 (Advisor)
- Kadir Cil, “Temperature Dependent Characterization and Crystallization Dynamics of Ge2Sb2Te5 in Films and Nanoscale Structures,” 12/2015 (Associate Advisor)
- Nicholas Williams, “Efficiency Enhancement of Micro-Thermoelectric Generators via Scaling and Minority Carrier Extraction,” 2/2016 (Associate Advisor)
- Lhacene Adnane, “High Temperature Characterization of Ge2Sb2Te5 Thin Films for Phase Change Memory Applications,”1/2011 – 10/2018 (Associate Advisor)
- Nafisa Noor, “Phase Change Memory Devices for Hardware Security,” 1/2015 – 3/2019 (Associate Advisor)
- Sadid Muneer, “Non-Equilibrium Non-isothermal Semiconductor Modeling and its Application to Phase Change Memory,” 8/2011 – 3/2019 (Major Co-Advisor)
- Jacob Scoggin, “Finite Element Modeling of Phase Change Materials and Devices,” 8/2014 – 8/2019 (Advisor)
- Raihan Khan, “Characterization and Mitigation of Resistance Drift in Amorphous Ge2Sb2Te5 Devices at Cryogenic Temperatures,” 1/2016 – 5/2021 (Advisor)
Current PhD Thesis Projects at UConn Nanoelectronics Laboratory
- Tashfique Kashem, “Modeling Composite Phase Change Devices,” 9/2018 – (Advisor)
- Hasan Talukder, “Nanoscale Devices for Hardware Security,” 1/2018 – (Associate Advisor)
- Saidjafarzoda Ilhom, “Atomic Layer Deposition of Electronic Materials” 8/2018- (Associate Advisor)
Current MS Thesis Projects (University of Connecticut, co-advised with Helena Silva)
- Elizabeth Baranovich, “Nanoscale Devices for Hardware Security,” 1/2019 – (Major Co-Advisor)
Selected Publications (UConn graduate and undergraduate students are in bold, PhD advisor underlined) (Link for the PDFs for all publications))
Electro-Thermal Phenomena at Nanometer Scale
Contributions include experimental demonstration of substantial thermoelectric heat flow in extreme (non-equilibrium) conditions, such as at solid-liquid interfaces at nanometer scale, and formulation of the energy exchanges associated with minority carriers.
- Bakan, N. Khan, A. Cywar, K. Cil, M. Akbulut, A. Gokirmak and H. Silva, ‘Self-heating of silicon microwires: Crystallization and thermoelectric effects,’ J. of Materials Research, 26: 1061-1071 (2011) (Invited Feature Paper).
- Bakan, N. Khan, H. Silva, A. Gokirmak, “High-temperature thermoelectric transport at small scales: generation, transport and recombination of minority carriers,” Nature Publications, Scientific Reports 3, 2724, doi:10.1038/srep02724 (2013) (Major contribution)
- Muneer, G. Bakan, A.Gokirmak, H. Silva, “Incorporation of GTR (generation–transport–recombination) in semiconductor simulations”, J. of Applied Physics, 129 (5), 055702 (2021) (Editor’s Pick)
Experimental Studies on Phase Change Memory Materials and Devices
Contributions include experimental characterization of Ge2Sb2Te5 phase change material from ~85 K to ~860 K, construction of high temperature Seebeck and Hall measurement setups, high-speed characterization techniques, and accelerating and stopping resistance drift with application of high electric fields at cryogenic temperatures.
- Cil, F. Dirisaglik, M. Wennberg, A. King, A. Faraclas, M. Akbulut, Y. Zhu, C. Lam, A. Gokirmak, H. Silva, “Electrical resistivity of liquid Ge2Sb2Te5 nanostructures,” IEEE Trans. on Elect. Dev. 60, 1, 433-437 (2013).
- Dirisaglik, G. Bakan, Z. Jurado, S. Muneer, M. Akbulut, J. Rarey, L. Sullivan, M. Wennberg, A. King, L. Zhang, R. Nowak, C. Lam, H. Silva, and A. Gokirmak, “High speed, high temperature electrical characterization of phase change materials: metastable phases, crystallization dynamics, and resistance drift,” Nanoscale, vol. 7, no. 40, pp. 16625–16630 (2015).
- Adnane, N. Williams, H. Silva, and A. Gokirmak, “High temperature setup for measurements of Seebeck coefficient and electrical resistivity of thin films using inductive heating,” AIP Rev. Sci. Instruments, vol. 86, no. 105119 (2015).
- Adnane, K. Cil, F. Dirisaglik, A. Cywar, C. Lam, A. Gokirmak, H. Silva, “High Temperature Electrical Resistivity and Seebeck Coefficient of Ge2Sb2Te5 Thin Films,” J. Appl. Phys., 122, 125104 (2017).
- Muneer, J. Scoggin, F. Dirisaglik, L. Adnane, A. Cywar, G. Bakan, K. Cil, C. Lam, H. Silva, and A. Gokirmak, “Activation Energy of Metastable Amorphous Ge2Sb2Te5 from Room Temperature to Melt,” AIP Advances 8 (6), 065314 (2018).
- Khan, F. Dirisaglik, A. Gokirmak, H. Silva, “Resistance drift in Ge2Sb2Te5 phase change memory line cells at low temperatures and its response to photoexcitation,” Appl. Phys. Lett. 116, 253501 (2020).
- Raihan Sayeed Khan, A Hasan Talukder, Faruk Dirisaglik, Helena Silva, Ali Gokirmak, “Accelerating and Stopping Resistance Drift in Phase Change Memory Cells via High Electric Field Stress,” arXiv preprint arXiv:2002.12487 (2020)
Construction of Computational Models for Phase Change and Ovonic Materials and Devices
Contributions include construction of temperature and electric-field dependent electro-thermal models integrated with dynamic materials models that capture nucleation, growth and amorphization during fabrication processes and device operation. We also demonstrated phase-change logic devices that utilize thermal cross-talk as a coupling mechanism using our computational models.
- A. Faraclas, G. Bakan, N. Williams, A. Gokirmak and H. Silva, “Modeling of Thermoelectric Effects in Phase Change Memory Cells,” IEEE Trans. on Electron Devices, 61, 2, 372-378 (2014).
- Z. Woods and Ali Gokirmak, “Modeling of Phase Change Memory: Nucleation, Growth and Amorphization Dynamics during Set and Reset: Part I – Effective Media Approximation,” Electron Devices, IEEE Trans., vol. 64, no. 11, pp. 4466-4471 (2017).
- Z. Woods, J. Scoggin, A. Cywar, L. Adnane, and A. Gokirmak, “Modeling of Phase Change Memory: Nucleation, Growth and Amorphization Dynamics during Set and Reset: Part II – Discrete Grains,” Electron Devices, IEEE Trans., vol. 64, no. 11, pp. 4472-4478 (2017).
- J. Scoggin, R. Khan, H. Silva, and A. Gokirmak “Modeling and Impacts of the Latent Heat of Phase Change and Specific Heat for Phase Change Materials,” Applied Physics Letters 112 (19), 193502 (2018).
- J. Scoggin, Z. Woods, H. Silva, and A. Gokirmak “Modeling Heterogeneous Melting in Phase Change Memory Devices” Applied Physics Letters 114 (4), 043502 (2019).
- J. Scoggin, H. Silva, A. Gokirmak, “Field dependent conductivity and threshold switching in amorphous chalcogenides—Modeling and simulations of ovonic threshold switches and phase change memory devices”, J. of Applied Physics, 128 (23), 234503 (2020).
- N. Kanan, R. S. Khan, Z. Woods, H. Silva, A. Gokirmak, “Phase‐Change Logic via Thermal Cross‐Talk for Computation in Memory”, Physica Status Solidi (RRL) – Rapid Research Letters, 15 (3) 2000422 (2021).
Nanoscale Silicon Transistors
Contributions include a high-sensitivity measurement technique to characterize nano-scale field effect transistors by utilizing ambient noise to overcome the quantization errors (Stochastic Resonance), design and implementation of ultra-low leakage and threshold voltage controllable nanoscale MOSFETs which utilize an additional gate structure surrounding the active area. We also demonstrated these MOSFETs with silicon nitride field isolation for integration with micro/nano-fluidic systems.
- A. Gokirmak and S. Tiwari, “Accumulated body ultranarrow channel silicon transistor with extreme threshold voltage tunability,” Appl. Phys. Lett., vol. 91, pp. 243504 (2007).
- A. Gokirmak, H. Inaltekin and S. Tiwari, “Attofarad resolution capacitance–voltage measurement of nanometer scale field effect transistors utilizing ambient noise,” IOP Nanotechnology, vol. 20, pp. 335203 (2009).
- M. Akbulut, H. Silva and A. Gokirmak, “Three-Dimensional Computational Analysis of Accumulated Body MOSFETs”, Nanotechnology, IEEE Trans., vol. 14, no. 5, pp. 847-853 (2015).
- M. B. Akbulut, F. Dirisaglik, A. Cywar, A. Faraclas, D. Pence, J. Patel, S. Steen, R. W. Nunes, H. Silva, A. Gokirmak, “Nanoscale Accumulated Body Si nMOSFETs,” Electron Devices, IEEE Trans., vol. 65, no. 4, pp. 1283 – 1289 (2018).