Research

Our group focuses on end-to-end modeling and characterization of electronic, optoelectronic, and bio-electronic devices, with an emphasis on their reliability physics. We look for system-level technological bottlenecks as new research topics and identify those problems whose solutions will illuminate the deeper physical principles involved. Our goal is the define  the "performance and reliability" potential of the technology for particular system-level applications.

In the past, we have worked on performance limits of resonant tunneling diodes and semiconductor lasers, theory of selective-area MOCVD crystal growth for optoelectronic ICs, mechanics of ALD crystal growth high-k dielectric deposition, and scaling limits of gate oxides and physics of oxide-semiconductor interface for MOSFET applications. For all these problems, we have developed new theoretical and computation tools to analyze the problems, worked closely with experimentalists to cross-check and verify our model predictions, and eventually encapsulated our understanding in broadly available tools for engineering design.

Currently, we are working on a series of research topics that reflect our vision for the semiconductor industry for the next 20-30 years, as follows:

Reliability Physics of Electron Devices and System

Our group is currently working on the self-heating and hot-carrier degradation in classical and emerging transistors, physics of moisture and ion transport in encapsulants, wirebond corrosion, fluid-stability of implanted nano-biosensors, and degradation kinetics of solar cells. The problems are practical and important, and our approach is grounded in fundamental physics, chemistry, and biology of the phenomena. See Papers for recent work on the topic. Also, the course on reliability physics for a broad introduction. 

Reliability of Oxide Semiconductor Transistors

As electronic devices continue to become more compact and energy-efficient, 3D integration technology has emerged as a potentially viable substitute for traditional 2D scaling. Our study is about Back-end-of-line (BEOL) thin-film transistors (TFTs) at the intermediate interconnect layers, employing oxide semiconductors. Central to our work is the study of reliability physics and modeling of these advanced materials and devices. Understanding the mechanisms that underpin the reliability of oxide semiconductors is crucial for ensuring their longevity and effectiveness in both logic and memory applications.

Atom-to-Farm Modeling/Reliability  of Solar Cells & Reading the Heartbeat of Solar Farms

Solar cells have long promised to deliver pollution-free inexpensive energy to satisfy the growing energy needs of the world.  In practice, only 1-5% of the energy needs is satisfied by solar energy. We are in the middle of an indepth analysis of every aspect of the  solar technology  to understand why solar cells are so inefficient/ expensive and what we can do about it. Our group has developed powerful analytical models for thermodynamic limits of solar cells, compact models for all the dominant technologies in the field, simulation tools for modules and optimization algorithms for solar farms.

Reliable Sensing with Unreliable "Wearable, Implantable and Environmental (WIE)" Sensors

Laboratory-based sensors have played a crucial role in healthcare and environmental monitoring for 50 years, offering improved selectivity and sensitivity. Challenges like high costs, limited access, and delayed results persist, leading to health risks like antibiotic-resistant super-bacteria outbreaks. To monitor chronic diseases effectively, a paradigm of autonomous smart sensors is being developed, promising timely interventions through wearable, implantable, and environmental (WIE) devices integrated with wireless technology and machine learning for real-time health monitoring and intervention. See Papers for recent contributions to the topic, and review Physics Principles of Nanobiosensors for an overview introduction.