Research Projects

Nanoelectronic Memristor/RRAM Devices for High Density Logic and Memory Applications: The 2-T nanoelectronic memristor/RRAM devices have gathered much research attention in the recent years for high density logic and memory applications [1-5]. This technology offers tremendous potential to address the scalability challenges beyond the end of Si- CMOS technology roadmap, as predicted by the ITRS. Gaining momentum from our rich expertise in the areas of successful high-k/metal gates based nanoscale CMOS technologies, our research in the areas of RRAM/memristor is specifically focused on understanding the transition metal oxide based 2-T devices for high density non-volatile memory (NVM) applications. Apart from developing a fundamental understanding on the mechanism of operation of these devices including: switching mechanism, charge storage mechanism, charge transport properties, voltage/current compatibility with CMOS, defects, and reliability issues, we are also working towards addressing the integration issues of these devices. Some of these integration issues include: exploring sustainable materials based devices, integration of appropriate metal electrodes with transition metal oxide, nanoscale patterning of electrodes, design and evaluation of adhesion promoter layer at oxide/metal interface in devices, understanding the process and device variability, yield, and repeatability, and development of intrinsic/isolation diodes. A schematic representation of high density RRAM/memristor in 1D1R crossbar memory architecture is shown in Figure 1. Our research activities typically involve device fabrication, electrical characterization, and understanding of the device physics, device modeling, and trend predictions.

Memristors as Biologically Inspired Synapse Links for Energy-Efficient Neuromorphic Computing: We have been working towards electrically studying the characteristics of our transition metal oxide memristor devices for applications as biologically inspired synapse links in novel neural circuits ( submitted our work to IEEE Electron Device Letters). A biological synapse is the connection between two neurons through which information signal transmits. How complicated are these biological synapse? Actually, they are very complicated with lots of factors involved in governing the conductance characteristics of a biological synapse [1,2]. How close are these memristors to a biological synapse? Well, ask this question to a neurophysiologist! But the good news is that the memristors do demonstrate certain characteristic of a biological synapse [3,4]. Researchers have demonstrated synapse functions on Si using CMOS VLSI circuits [5,6]. However, a major challenge with CMOS synapse lies in matching the power efficiency and area requirement, especially because billions of these synapse will be needed on chips for neuromorphic computing. Memristor devices offer tremendous advantages in terms of providing low power consumption, and tremendous densification opportunities. Our research is extensively focused on understanding the synapse characteristics of memristors from device perspective and work closely with neurophysiologist and circuit experts for application development.

Sustainable Photovoltaic Technologies: The third generation of Solar cells based on inorganic nanostructures has been projected to overcome the fundamental efficiency limits of c-Si solar cells. Our research group collaborates with the researchers at UT-PVIC to investigate nanomaterials based next-generation of photovoltaic devices. We investigate sustainable Carbon Nanotube (CNT) and Si-nanowire/nanoparticles based solution process-able solar cells. Our specific focus lies in understanding the interface between: (i) nanomaterials and metal electrodes, (ii) transport of charge carriers through nanomaterials, (iii) defect states and passivation techniques, (iv) novel device structures for integrating and harnessing the unique properties of nanomaterials. We accomplish these studies by developing and implementing advanced electrical characterization techniques based on Admittance-Spectroscopy, and Temperature Dependent Current-Voltage measurements on photovoltaic devices.

Admittance-Spectroscopy based characterization of CdS/ CdTe Solar Cells: Our research group actively collaborates with Prof. Alvin Compaan’s group in the department of Physics and Astronomy to understand the various interface properties in CdS/CdTe Solar cells using Capacitance-Voltage based measurement. We are also working collaboratively to develop novel technologies for CdS-CdTe solar cells that have potential to achieve high efficiency and better reliability with easier and more cost-effective fabrication techniques than currently available.

TCAD Simulation of Devices : The current focus of this research is to understand the fundamental properties of thin films PV and OPV devices using TCAD OMNI simulation software. The simulation software is capable of simulating PV devices with and without the optical illumination. The material parameters of the organic semiconductor are extracted from experiments, published literature, and material models. After the optimization of materials, the research evaluates novel device structures to improve the devices performance.