Research

Current Topics of Interest


A. Ultra Low Power Electronics

The unprecedented technological success of the electronics industry over the last five decades have been driven by Silicon (Si) technology at the center of which resides the metal oxide semiconductor field effect transistor (MOSFET). Relentless scaling of MOSFET dimensions ensured faster and cheaper computing since more and more transistor could be packed into the same chip area. At the same time scaling of supply voltage kept the power density practically constant. This golden era of MOSFET scaling is often referred to as the Dennard Scaling era. However, around 2005, the voltage scaling almost stopped owing to non-scalability of the subthreshold swing (SS) to below 60mV/decade resulting from Boltzmann statistics.  Although voltage scaling stopped, length scaling still continued for another decade albeit with new challenges like increasing power density, short channel effects and increasing parasitic. Unfortunately, even for the most advanced FinFET technology length scaling seems extremely challenging at present. Therefore, it is imminent that both aspects of MOSFET scaling will end very shortly. In order to sustain the growth of the semiconductor industry, it is necessary that novel low power beyond Boltzmann device concepts based on aggressively scalable materials be conceived immediately.

1. Strain Field Effect Transistors (SFET)

Das, S. Scientific Reports, 6, 34811, (2016). 

2D strain field effect transistor or 2D-SFET, allows sub-60 mV/decade subthreshold swing (SS) and considerably higher ON current compared to any state of the art FETs. Additionally, by the virtue of its ultra-thin body nature and electrostatic integrity, the 2D-SFET enjoys aggressive channel length scaling. The 2D-SFET works on the principle of voltage induced strain transduction. It uses an electrostrictive/piezoelectric material as gate oxide which expands in response to an applied gate bias and thereby transduces an out-of-plane stress on the 2D channel material. This stress reduces the inter-layer distance between the consecutive layers of the semiconducting 2D material and dynamically reduces its bandgap to zero i.e. converts it into a semi-metal. Thus the device operates with a large bandgap in the OFF state and a small or zero bandgap in the ON state. As a consequence of this transduction mechanism, internal voltage amplification takes place which results in sub-60 mV/decade SS.

2. Excitonic Field Effect Transistors (ExFET)

Excitons are physically separated but electrostatically bound electron-hole pairs. As such exciton mass is several orders of magnitude lower than any atom which facilitates formation of high temperature Bose condensate leading to superconductivity. The major roadblock towards the realization of room temperature excitonic condensates has been their relatively short lifetime (one of the dominant lifetime limiting mechanism being the electron-hole recombination). Such limitations, however, can be overcome by spatially separating electrons and holes, and yet maintaining their Coulombic attraction using stacked and individually gated 2D TMDC materials in ExFET geometry.

3. Tunneling Field Effect Transistor (TFET)

Das, S. et al. A. ACS Nano 8(2), 1681-89, (2014).

TFETs operate by quantum mechanical band to band tunneling of charge carriers, and thereby allow sub-60mV/decade SS at room temperature. However, TFETs suffer from low ON current owing to lower transmission probability through the semiconductor band gap, which could be compensated by the ultra-thin nature of nanomaterials which reduces the tunneling distance.

 


B. Novel Devices for Artificial Intelligenc

Synaptic Devices

Stochastic Devices

Neuromorphic Devices


C. Devices for Internet of Things

Sensors

Photodetectors and Photoemitters

Display Electronics

Glasstronics

Flexible Electronics


D. Contact Engineering for Nanomaterials

Fermi-level Depinning in Metal/2D Contacts

Contact Scaling

Thermal Reliability of Contacts


E. Electrochemistry of 2D Materials

Corrosion

Monolayer Synthesis via Electro-Ablation (EA)

Electrochemical Polishing

Defect Engineering


F. Cryptography and Cyber Security


G. Radiation Impact on 2D Materials and Devices