We worked on the system of h-BN encapsulated single layer Graphene, which was placed under high magnetic field (8-10 Tesla) and at low temperatures (~ 20 mK range). The interaction of the electrons in the 2-dimensional sheet with the external perpendicular magnetic field gave rise to Quantum Hall Effect (QHE) in the system. We studied different aspects of QHE in graphene systems using electrical noise measurement spectroscopy (thermal noise and shot noise) as the probe. 

The three main aspects that we focused on were:

• Quantum heat transport measurements (thermal noise) in the low-energy - integer and fractional QHE regime 

• Understanding nature of electrical fluctuations (shot noise) due to electrostatically gated quantum dot formed by Integer quantum hall point contacts (QPC) in Graphene systems 

• Breakdown of electron-interaction-driven integer QHE, due to non-equilibrium processes 

We worked on the system of two-dimensional (2D) Van der Waals heterostructures. In this system, we focused on the class of hBN-encapsulated Twisted-Bilayer Graphene (TBG), where one sheet of graphene is placed over another sheet and there is a relative twist angle between the two layers. Researchers have observed that if the twist angle between the layers is high (>3-4 degrees), then the two layers are decoupled. However, as the twist angle is reduced to lower angles, especially (~ 1 degree), the two layers couple with each other and form a Moiré system. The band structure of the system changes and strong electron-electron interactions develop in the system, leading to development of correlated  phases. 

We wanted to understand the properties of this system of TBG by using thermoelectric transport measurements as our probe. We were mainly interested in 

(a) Identifying dominant thermoelectric transport mechanisms in TBG systems having different angles and 

(b) Understating the thermoelectric transport properties of the correlated phases developed in low angle (0.1, 0.5, 1.25, 1.6 degrees) TBG samples. 

We worked on Gallium Nitride (GaN: Group-III - Nitride) based wide bandgap semiconductors where we focused on two device structures, High Electron Mobility Transistors (HEMTs) and Ultra-Violet Photodetectors (UV-PDs). In these devices, we focused on the Schottky metal semiconductor contacts. We were trying to (a) investigate and (b) resolve the issues developed at the metal-semiconductor interface due to electronic surface states (or trap states), which were causing degraded device performance. As a solution, we worked on improving the surface electrical properties of the semiconductor by adsorption of a single layer of functionalized Organic Molecules, by the process of Self-Assembled Monolayers. 

We had demonstrated a significant enhancement in the electrical characteristics of different Schottky diodes on both GaN films and AlGaN/GaN HEMT heterostructures by using this novel process. Through this approach, we had also presented a significant enhancement in the performance of both biased and self-powered GaN-based MSM UV PDs.