Our group is involved in developing novel nanotechnology solutions to the challenges facing giga- and tera-scale integration. This includes using new physical concepts, new materials, creative devices, circuits and architectures to improve system functionalities in the existing semiconductor technologies and implement completely new nano-systems for maximum benefit.

The last few decades have witnessed an unprecedented growth in the performance of the CMOS technology that now has a market share of more than $270 billion. This era also witnessed many new circuits and system concepts to support the momentum of growth in the industry. However, now electrical engineering is at its crossroads. Research in nanoelectronics must undergo a paradigm shift as the CMOS scaling approaches its ultimate limits. The next decade will usher us into an era of new science and disruptive technologies. Research involving the integration of various novel concepts – from new materials to new architectures – is necessary for enabling unique functionality beyond just high-performance general-purpose computing.

From the many research frontiers now expanding, we are specifically working in two areas: (i) terahertz wireless communication to meet the exploding bandwidth demands of the consumers and (ii) developing device and circuits concepts for computing with magnets, which offer the ultimate thermodynamic limits of computation governed by Landauer’s principle.

CURRENT RESEARCH:


Computing with magnets

next-gen2
In the last several decades, productivity of the semiconductor technology has increased by a factor of more than a billion. The rapid growth in the semiconductor industry is a direct result of dimensional scaling allowing for microprocessor chips to pack more functionality per cost. However, we are now at the 7nm node (IBM) and continued scaling would only mean more leakage, resulting in an exponential increase in power dissipation. Hence the need of the hour is a beyond CMOS technology that overcomes the hurdles imposed by scaling constraints.

The discovery of the Giant Magnetoresistance (GMR) in 1988 paved the way for spintronics based devices like Magnetic Tunnel Junctions (MTJ) and Magnetic RAMs, and since then spintronics has become a fast emerging frontrunner in this race of beyond CMOS technologies. The use of electron spin, rather than its charge, gives spintronics devices an additional degree of freedom. Among the potential alternatives, devices based on nanoscale magnets in the field of spintronics have received special attention thanks to their advantages in terms of robustness and enhanced functionality. Magnets are non-volatile: their state remains even if the power to the circuit is switched off. Thus, the circuits do not consume power when not used – a very desirable property for modern tablets and smart phones. Virtually near-zero leakage, high integration density and high speeds have made such devices very popular.
We at the Quantum Nanoelectronics Lab at NYU are involved in analyzing the underlying physical principles of nanomagnets and their dynamics, and developing spintronics based magnetic memories and logic devices. By running Monte Carlo simulations for the magnetization dynamics of nanomagnets, we hope to understand the complex interplay between the injected spin current, the pulse duration, the probability of switching, the delay and the energy involved, among other quantities. We are attempting to build an analytical model of the switching mechanisms of nanomagnets, which will allow us to create faster low-power spin-transfer torque MRAMs.

Another facet of our research involves using Giant Spin Hall Effect (GSHE) logic devices for stochastic computing. We are currently developing compact scalable models for stochastic nanomagnet dynamics in the GSHE switch, which will allow us to create a suite of magnetic switches in a stochastic spin library (SSL) containing the timing, energy, and error probability descriptions of spintronic standard cells.

Sub-THz Materials

Our group is involved in developing novel nanotechnology solutions to the challenges facing giga- and tera-scale integration. This includes using new physical concepts, new materials, creative devices, circuits and architectures to improve system functionalities in the existing semiconductor technologies and implement completely new nano-systems for maximum benefit.

Journal Articles


CitationResearch AreasDate
V. Petrov, D. Moltchanov, M. Komar, A. Antonov, P. Kustarev, S. Rakheja, and Y. Koucheryavy. "Terahertz Band Intra-Chip Communications: Can Wireless Links Scale Modern x86 CPUs?". Accepted for publication in IEEE ACCESS. doi: 10.1109/ACCESS.2017.2689077iii-nitride2017/04/11
K. Li, S. Rakheja. Optimal III-nitride HEMTs: From Materials and Device Design to Compact Model of the 2DEG Charge Density. In SPIE Proceedings: Gallium Nitride Materials and Devices XII, vol. 10104, p. 1010418-1 – 1010418-16, Feb. 2017.iii-nitride2017/02/01
S. Rakheja. On the Gaussian Pulse Propagation Through Multilayer Graphene Plasmonic Waveguides – Impact of Electrostatic Screening and Frequency Dispersion on Group Velocity and Pulse Distortion. IEEE Transactions on NanoTechnology, vol. 15, no. 6, pp. 936–946, Nov. 2016. Terahertz Band Via Graphene2016/11/01
S. Rakheja and D. Antoniadis. MIT MVS Modelsiii-nitride2016/04/11
S. Rakheja and P. Sengupta "The Tuning of Light-Matter Coupling and Dichroism in Graphene for Enhanced Absorption: Implications for Graphene-based Optical Absorption Devices" Journal of Physics D: Applied Physics, vol. 49, no. 11, p. 115106, 2016. Terahertz Band Via Graphene2016/01/24
S.Rakheja and P. Sengupta "Gate-Voltage Tunability of Plasmons in Single-layer Graphene Structures - Analytical Description, Impact of Interface States, and Concepts for Terahertz Devices" IEEE Transactions on Nanotechnology, vol. 15, no. 1, pp. 113-121, Jan. 2016. Terahertz Band Via Graphene2016/01/01
S. Rakheja and P. Sengupta "Design of Graphene-based Optical Modulators via Tuning of Surface Plasmon Resonance and Dielectric Constants" In Materials Research Society (MRS) Meeting, Boston, Massachusetts, Nov. 29 – Dec. 04, 2015. Terahertz Band Via Graphene2015/11/29
S.Rakheja, M. Lundstrom, and D. Antoniadis. An Improved Virtual-Source-Based Transport Model for Quasi-Ballistic Transistors – Part II: Experimental Verification. IEEE Transactions on Electron Devices, vol. 62, no. 9, pp. 2794–2801, Sep. 2015.iii-nitride2015/09/01
S. Rakheja, “Fundamental Limits of Energy Dissipation in Spintronic Interconnects Using Optical Spin Pumping,” NANOARCH, July 8-10, 2015.Next Generation Electronics2015/07/08
C. N. Barati, S. A. Hosseini, S. Rangan, P. Liu, T. Korakis, S. S. Panwar, and T. S. Rappaport, “Directional Cell Search for Millimeter Wave Cellular Systems,” Proc. IEEE Signal Processing Advances in Wireless Communications (SPAWC), Toronto, Canada, pp. 120{124, June 2014.initial access, Low-Power Fully Digital Transceivers, mmWave MAC, Network Design2014/06/22
P. Bonhomme, S. Manipatruni, R. Mousavi, S. Rakheja, D.E. Nikonov, I.A. Young, A. Naeemi, “Circuit simulation of magnetization dynamics and spin transport,” IEEE Transactions on Electron Devices, vol. 61, no. 5, May 2014.Next Generation Electronics2014/03/28
S. Rakheja, A. Naeemi, “Communicating novel computational state variables in post-CMOS logic”, IEEE Nanotechnology Magazine, vol. 7, no. 1, 2013.Next Generation Electronics2013/02/05

Conference Papers


CitationResearch AreasDate
R. Pujari, S. Rakheja "Performance Evaluation of Copper and Graphene Nanoribbon in 2D Network-On-Chip Structures" In The 18th International Symposium on Quality Electronic Design (ISQED), Santa Clara, California, March 13 – 15, 2017. Terahertz Band Via Graphene2017/03/13
S. Rakheja "Communication Limits of On-Chip Graphene Plasmonic Interconnects" In The 18th International Symposium on Quality Electronic Design (ISQED), Santa Clara, California, March 13 – 15, 2017. Terahertz Band Via Graphene2017/03/13
S. Farzaneh, S. Rakheja "Plasmon Propagation in Gated Bilayer Graphene" In The International Society for Optics and Photonics (SPIE) – Photonics West, San Francisco, California, Jan. 28 – Feb. 02, 2017. Terahertz Band Via Graphene2017/01/28
S. Rakheja, P. Sengupta, K. Li. Challenges and Opportunities in Modeling Gallium Nitride High Electron Mobility Transistors – From Numerical Simulations to Compact Transistor Model. In International Workshop on Nitride Semiconductors (IWN), Orlando, Florida, Oct. 02 07, 2016.iii-nitride2016/10/02
S. Rakheja and D.A. Antoniadis. Physics-based Compact Modeling of Charge Transport in Nanoscale Electronic Devices (invited). In IEEE Electron Devices Meeting (IEDM), Washington D.C., Dec. 07 – 12, 2015.iii-nitride2015/12/07
S.Rakheja, M.Lundstrom, and D.Antoniadis. An Improved Virtual-Source-Based Transport Model For Quasi-Ballistic Transistors – Part I: Capturing Effects of Carrier Degeneracy, Drain- Bias Dependence of Gate Capacitance, and Non-Linear Channel-Access Resistance. IEEE Transactions on Electron Devices, vol. 62, no. 9, pp. 2786–2793, Sep. 2015.iii-nitride2015/09/01
V. Kumar, S. Rakheja, A. Naeemi "High-Frequency Models for Multilayer Graphene Interconnects," In International Microwave Symposium (IMS), Phoenix, Arizona, May 17 – 22, 2015. Terahertz Band Via Graphene2015/05/17
O. Orhan, E. Erkip, S. Rangan, "Low Power Analog-to-Digital Conversion in Millimeter Wave Systems: Impact of Resolution and Bandwidth on Performance" Proc. Information Theory and Applications Workshop (ITA), Proc. ITA, San Diego, Feb. 2015Low-Power Fully Digital Transceivers, mmwave2015/02/01
S. Rakheja, M. Lundstrom, and D.A. Antoniadis. A Physics-Based Compact Model for FETs from Diffusive to Ballistic Carrier Transport regimes. In IEEE Electron Devices Meeting (IEDM), San Francisco, California, Dec. 15 – 17, 2014.iii-nitride2014/12/15