[paper] 2D-SFET Based SRAMs

Niharika Thakuria, Graduate Student Member, IEEE, Daniel Schulman, Member, IEEE, Saptarshi Das, Member, IEEE, and Sumeet Kumar Gupta, Member, IEEE

2D Strain FET (2D-SFET) Based SRAMs - Part I: Device-Circuit Interactions

 IEEE TED, vol. 67, no. 11, pp. 4866-4874, Nov. 2020

DOI: 10.1109/TED.2020.3022344.

Abstrat: In this article, we analyze the characteristics of a recently conceived steep switching device 2-D Strain FET (2D-SFET) and present its circuit implications in the context of 6T-SRAM. We discuss the dependence of 2D-SFET characteristics on key design parameters, showing up to 2.7× larger ON-current and 35% decrease in subthreshold swing when compared to 2D-FET. We analyze the performance of 2D-SFET (as drop-in replacement for standard 2D-FET) in 6T-SRAM for a range of design parameters and compare those to 2D-FET 6T-SRAM. 2D-SFET 6T-SRAM achieves up to 5.7% lower access time, 63% higher write margin, and comparable hold margin, but at the cost of comparable to 11% lower read stability and 16% increase in write time. In Part II of this article, we mitigate the read stability issues of 2D-SFET SRAMs by proposing VB-enabled SRAM designs.

Fig: 2D-SFET model with bandgap reduction and 2-D-electrostatics [18]. COX, CGS/D,F, CIT, and CGB are oxide, gate (G) to source (S)/drain (D) fringe, trap, and PE capacitance, respectively. VFB, and VFBS are flat-band voltage of G and back contact. VQFL(VS,VD) is S/D quasiFermi level. ΔEG(VG'B) is VGB dependent bandgap change, τEG is strain transduction delay, and REG is resistance used to model τEG. ΔEG(τEG) is final bandgap reduction considering τEG, used for calculating channel charge, QCH(ΔEG(τEG)).

Aknowlegement: This work was supported in part by NSF under Grant 1640020, in part by Nanoelectronics Research Corporation (NERC), and in part by Semiconductor Research Corporation (SRC) under Grant 2699.003

[CAS Seasonal School] How Technology is Impacting Agribusiness

How Technology is Impacting Agribusiness

A CAS seasonal school on technology and agribusiness will be held virtually from November 16th to November 20th. The program is quite interesting and we invite you to register through our web page www.asic-chile.cl. Registration is free.

The current world population of 7.6 billion is expected to reach 9.8 billion in 2050. According to the United Nations Food and Agriculture Organization (FAO) global agricultural productivity must increase by 50% – 70% to be able to feed the world population in 2050. Other researchers consider that reducing the waste of food would be enough.

Factors if not obstacles to be considered to meet global food demand by 2050 and beyond:

• Less arable land: As cities are growing, the space allowed to agriculture is shrinking.
• Climate change: Impacting dramatically agribusiness.
• Role of the agribusiness on the GHG emissions.
• Planet boundaries and the role of agribusiness.
• Availability of freshwater.
• Soil degradation.

The need has never been greater for innovative and sustainable solutions and technology should lead to significant improvement in our food and nutritional security.

In this seasonal school prestigious researchers and experts from all over the world will present the problems and challenges agribusiness is facing and how technologies such as IoT, AI, Machine Learning, sensors, electronic circuits, electronic systems, ICs, etc., can be applied to improve and solve the majority of those problems.

This is the first of a series of “Technology and Agribusiness” Seasonal Schools. It will be a meeting point for professionals working on Precision and Smart Agriculture, as well as professionals working on IoT, sensors, electronic circuits, electronic systems, ICs, etc.

We invite you to participate in this first version of the Technology and Agribusiness Seasonal School, which due to the pandemic will be 100% online and free of charge.

Join us!

[paper] Organic semiconductor (OSC) OFETs

Boyu Peng, Ke Cao* Albert Ho Yuen Lau, Ming Chen, Yang Lu* and Paddy K. L. Chan

Crystallized Monolayer Semiconductor for Ohmic Contact Resistance, High Intrinsic Gain, and High Current Density

Adv. Mater. 2020, 32, 2002281 

DOI:10.1002/adma.202002281

Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road (HK)

*Department of Mechanical Engineering, City University of Hong Kong, Kowloon (HK)

Abstract: The contact resistance limits the downscaling and operating range of organic field-effect transistors (OFETs). Access resistance through multilayers of molecules and the nonideal metal/semiconductor interface are two major bottlenecks preventing the lowering of the contact resistance. In this work, monolayer (1L) organic crystals and nondestructive electrodes are utilized to overcome the abovementioned challenges. High intrinsic mobility of 12.5 cm2 V−1 s−1 and Ohmic contact resistance of 40 Ω cm are achieved. Unlike the thermionic emission in common Schottky contacts, the carriers are pre- dominantly injected by field emission. The 1L-OFETs can operate linearly from VDS = −1 V to VDS as small as −0.1 mV. Thanks to the good pinch-off behavior brought by the monolayer semiconductor, the 1L-OFETs show high intrinsic gain at the saturation regime. At a high bias load, a maximum current density of 4.2 µA µm−1 is achieved by the only molecular layer as the active channel, with a current saturation effect being observed. In addition to the low contact resistance and high-resolution lithography, it is suggested that the thermal management of high-mobility OFETs will be the next major challenge in achieving high-speed densely integrated flexible electronics.

Fig: a) Schematic charge accumulation and b) output curves of short-channel OFETs. c) Schematic charge accumulation and d) output curves of source-gated transistors. e) Schematic charge accumulation and f) output curves of 1L-OFETs. 

Acknowledgements: The authors gratefully acknowledge the support from the General Research Fund (GRF) under Grant Nos. HKU 17264016 and HKU 17204517, University of Hong Kong Seed Funding Grant Nos. 201711159068 and 201611159208. The authors appreciate Prof. Xin Cheng and Xin Zhuang from Southern University of Science and Technology for their support on e-beam lithography. The authors also thank Dr. Hagen Klauk and James W. Borchert for the fruitful discussions and suggestions.

[paper] Compact Modeling of Organic TFT

Jakob Pruefer, Jakob Leise, Ghader Darbandy, Aristeidis Nikolaou, Hagen Klauk, James W. Borchert, Benjamín Iñíguez, Fellow, IEEE, Thomas Gneiting, Member, IEEE

and Alexander Kloes, Senior Member, IEEE

Compact Modeling of Short-Channel Effects in Staggered Organic Thin-Film Transistors

IEEE Transactions on Electron Devices, vol. 67, no. 11, pp. 5082-5090, Nov. 2020

DOI: 10.1109/TED.2020.3021368.

Abstract:This article introduces analytical compact models of short-channel effects in staggered organic thinfilm transistors (TFTs). The effects of subthreshold-swing degradation, threshold-voltage roll-off, and drain-induced barrier lowering (DIBL) on the static current–voltage characteristics of staggered TFTs are extracted from an analytical potential solution of the 2-D problem of the staggered geometry. This solution is derived by using the Schwarz–Christoffel transformation that leads to a complex mapping function linking the staggered geometry to an equivalent in another coordinate system for which an analytical potential solution exists. The commercial TCAD is used to verify the compact models. Finally, the closed-form and physics-based equations are incorporated into an existing compact current model and verified by measurements on staggered organic TFTs with channel lengths as small as 0.4 µm fabricated on flexible plastic substrates by stencil lithography.

Fig:(a) Schematic cross section and (b) simplified geometry 

of the staggered organic TFTs for the TCAD simulations.

Acknowledgement: This work was supported in part by the German Federal Ministry of Education and Research under Grant 13FH015IX6 Strukturnahe Modellierung organischer flexibler KurzkanalTFTs (Structure-Oriented Modeling of Organic FLEXible short-channel TFTs) (SOMOFLEX), in part by the EU H2020 Marie Sklodowska-Curie actions (MSCA) Research and Innovation Staff Exchange (RISE) Project Design Oriented ModellINg for flexible electrOnics (DOMINO) under Grant 645760, and in part by the German Research Foundation (DFG) under Grant KL 1042/9-2 (SPP FFlexCom). 

[paper] Capacitive Sensor for Dental Implants

Alireza Hassanzadeh, Ali Moulavi and Amir Panahi

A New Capacitive Sensor for Histomorphometry Evaluation of Dental Implants

in IEEE Sensors Journal, 

DOI: 10.1109/JSEN.2020.3026745

Abstract: Knowing information about the internal functions of the human body has always been the subject of scientific research. Processing of the data from inside of the body gives access to valuable information for the therapist. In this paper, an implantable capacitive sensor has been designed and implemented inside the bone to evaluate the new bone growth. Reducing the medical x-ray imaging dose during a jaw scan is a motivation for the design of the sensor. The new capacitive sensor can replace multiple x-ray imaging sessions. Low energy consumption, stable performance, and information processing rate are some of the engineering challenges for implanted sensors. The designed sensor is a zero power module, which can easily be implemented in dental tooth implants without any active component. The capacitive sensor information can be transmitted to a reader device via a wireless inductive link. The sensor simulation results from a commercial software confirm experimental measurements. The fabricated sensor has been tested on the femur (thigh) bone and mandible bone (lower jaw). The sensor capacitance changes from 20nF to 1.57μF for the fabricated sensor and amount of the surrounding bone. Fabrication results show that variation of sensor capacitance from the early stage of the dental implant to full recovery and bone development is more than seven times. The wide range of sensor capacitance variation allows for better bone development characterization. 

Fig: a) Schematic of a typical sensor and reader inductive link, b) Reader and the implanted sensor.