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For development and implementation of analog computing system, recently, Brain inspired computing, also known as nueromorphic computing has received much attention as it exhibits many features needed for design and development of energy efficient, fast and, highly parallel analog computing system. However, like all other new and emerging technologies, neuromorphic computing is also facing difficulties and challenges in terms of hardware design and implementation [3]-[4]. Hence, in this project we are focusing to generate indigenous tools which can be further used to solve the challenges in brain inspired electronics system design.

The Aim of this project is to design, develop and fabricate an integrated frequency multiplier utilizing a novel self-switching diode (SSD) based on GaN two-dimensional heterostructures. The SSD has an entirely different working principal which does not require any p-n junction and /or Schottky barrier to operate eliminating the requirement of an additional bias circuit than that of conventional and commercially available diodes. Due to planar and single-layered device architecture, SSD exhibits low parasitics resulting in a zero-bias rectification up to 1.5 THz at room temperatures with responsivity and NEP comparable to commercially available Schottky diodes. The SSD can easily be fabricated utilizing a single-step lithography followed by an etching process from using wide variety of materials varying from conventional Silicon to III-V heterostructures to novel graphene. On the other hand, commercially available Schottky barrier diodes, have multi-layered and vertical structure, and require an additional bias high enough to overcome the built-in electric field and to allow current flow. It further introduces the parasitic capacitance which in turn limits the operating speed and high frequency performance restricting to utilise a Schottky diode to generate very high microwave/ Terahertz frequencies. Schottky barrier diodes are commonly being utilised in array i.e. parallel or anti-parallel configuration for frequency multipliers to improve input/output power handling capacity. However, they suffer from excessive heat at the Schottky junctions leading to the performance degradation and require novel materials and challenging fabrication techniques to achieve ultra-low charge carrier transit time and parasitics at room temperature to generate high microwave/terahertz signals. Utilising excellent properties of GaN, SSD can be implemented for frequency multipliers to generate signals with hundreds of gigahertz frequencies with improved efficiency and high power handling capacity. Planar structure of device is more suitable as more number of SSDs in array configuration can be easily integrated without interconnects reducing overall device impedance exhibiting better noise properties at high frequencies. Further, heat dissipation can be managed efficiently by correct design of SSD channel. Therefore, developing GaN SSD based integrated frequency multiplier is timely given the rapid progress in the GaN technology and development of high frequency microwave/terahertz sources for wide variety of applications such as future generation communications, medical and security imaging etc. Additionally, training of early career researchers in this project will provide India with the scientists and engineers with the skills to transfer GaN-based technologies from academia to industry for industrial and/or strategic applications in line with Government of India’s Semiconductor Mission, Make in India, Aatmnirbhar Bharat, and Skill India Missions.

The aim of this project is to design and develop a novel nanoelectronic rectifier, also known as self-switching diode (SSD), from van der Waals hetrostructure consisting of graphene/h-BN/MoS2 layers. Due to excellent material properties, proposed SSDs can operate with ultra-fast switching speed than that of electronic rectifiers fabricated from conventional semiconductors for a wide variety of applications such as signal detection, future generation communications, medical and security imaging etc. Recently, emerging two-dimensional (2D)-layered semiconductors including graphene, hexagonal boron nitride (h-BN) and molybdenum disulphide (MoS2) have shown considerable potential for designing next-generation integrated electronic and optoelectronic devices, due to their excellent unique physical and structural properties. Particularly, the 2D-layered semiconductors of graphene, h-BN and MoS2 can be flexibly combined to form different configurations of vertical van der Waals heterostructures with atomically sharp interfaces and tunable band alignment, opening up vast opportunities for fundamental investigation of novel electronic properties at the limit of single atom thickness and potential applications in novel devices concept such as self-switching diode. The working of conventional rectifying diodes depend either upon a pn doped junction or a Schottky barrier, that also determines the limitations. An applied bias high enough is generally required to overcome the built-in electric field and to allow a significant current flow, introducing the parasitic capacitance which in turn limits the operating speed and high frequency performance. The novel nanodiode concept proposed in this project is entirely different and it has a single‐layered device architecture that is ideally‐suited to graphene and/or graphene based van der Waals heterostructures. Moreover, it operates on new working principle enabling zero threshold voltage, thus eliminating the need for a bias circuit. Developing SSD in graphene/h-BN/MoS2 is timely given the rapid progress in graphene and/or 2d van der Waals material engineering. Since the device speed generally scales with the carrier mobility, the proposed SSDs are expected to operate at very high frequencies possibly up to THz.

In this research, a semi-classical drift-diffusion 3D modeling have been developed to predict the rectification behavior and noise spectra of both the ballistic rectifiers considered in this research. Furthermore, the developed model predicts that minimum low frequency noise for both the devices which depends upon carrier concentration inside device active region rather than mobility, enables potential applications as THz detectors for imaging.

Further, it has been demonstrated that symmetric geometry of both type of ballistic rectifiers, i.e. three terminals and four terminals, can be utilized as a thermoelectric rectifier for wide variety of applications to produce rectified output voltage converting thermal energy radiated from the electronic devices/ICs. Prototypes of ballistic rectifiers with and without antidot have been developed demonstrating rectification of microwave/RF signals.

The development of this novel technology of Ballistic Rectifier can be used for various applications including future generation communications, signal detection, medical and security imaging.

This research highlights the high power GaN HEMT technology for the high frequency applications. Semi-insulating SiC substrates are used for optimal performance at higher temperatures. This technology features high performance, high power density, high gain and high efficiency at microwave frequencies. We have reported on the simulation and modelling of GaN transistor and its performance relevant to applications ranging from high power, high frequency and high bandwidth. Additionally, we have analyzed the noise characteristics and cut-off frequencies of the device.

The demand for materials based on nanotechnology has been identified as an essential component in a variety of applications. Among other applications, nano-based sensing devices have received considerable attention, especially in medical and environmental monitoring. Recent developments have enabled the fabrication and application of sensing devices. My research talk will consist of the basic concepts of the fabrication of different modified electrode based sensor. Similarly, the fabrication of bacteria sensor associated with urinary tract infections, herbicide atrazine, and electrochemical determination of cancer biomarker sensors will also be presented, highlighting its advantages over other conventional sensors, as reported by my recent publication. Flexible consumer electronic products, such as folding displays, health monitoring devices, smart fabrics, and flexible body sensors, have gotten a lot of attention since they can be utilised for flexible and wearable electronic gadgets. Lightweight, flexible, and large storage capacity are all requirements for an energy storage system to power these functional devices. Flexible supercapacitors, with their high power densities, extended life, and quick charge/discharge rates, have been highlighted as a possible solution for such needs. I am currently working on the development of high energy density conducting polymer based supercapacitor for energy storage applications. Energy conversion (EC) devices that are environmentally friendly and efficient are critical for the production of sustainable energy. Direct methanol fuel cells (DMFCs) are potential EC devices for supplying power to portable electronic devices and electric vehicles, with the slow methanol electrooxidation reaction (MEOR) kinetics at the anode being the main constraint. Platinum (Pt) is typically the most advantageous choice for electrocatalysis in the MEOR due to its distinct d-band configuration, which allows for rapid methanol adsorption and dissociation. However, the high cost and proclivity to poison render widespread commercial Platinum (Pt)-based electrocatalysis in DMFCs unviable. My attempt is to rationally integrate Copper, Nickel and Cobalt based materials in order to create a novel composite that could be used effectively in DMFCs. Hydrogen has been recognised as a future fuel that could help solve the energy crisis caused by fossil-fuel exhaustion. The most abundant element in the universe is hydrogen. Hydrogen has a higher combustion enthalpy and produces zero-pollution. Hydrogen (H2) fuel cells have a lot of potential in transportation and stationary applications, but their widespread commercialization is hampered by their expensive cost. Because platinum (Pt) is one of the most expensive components of a fuel cell, numerous R&D efforts have focused on ways to improve the activity, as well as platinum free catalysts for long-term applications. My research project also focuses on two ways to addressing catalyst challenges: low-Pt catalysts and Pt-free catalysts.