First-principles method is a powerful approach to study atomic scale physics and deals with fundamental physical processes. With its introduction into thermal transport area, the quantum description of quantized lattice vibrations, phonons, achieved great success in predicting/explaining thermal transport properties in the past two decades. However, frontier technologies based on solid-state systems and devices will soon meet the boundary of our usual understanding of energy transport. Our pursuit of faster computing, higher energy efficiency and better sustainability requires major advancements in the study of quantum energy transport. Our research on phonon dynamics and thermal transport then has both technological and scientific importance that could lead to discovery of novel transport phenomena and disruptive technology strategies.
My PhD research is motivated by the following challenges in our community:
My research aims to tackle the challenges above along these directions:
Limits of Energy-Efficient Computing
Nonequilibrium carrier transport
High temperature thermal transport
Temperature-dependent optical responses
[Community software: FourPhonon](https://zrhan.notion.site/Community-software-FourPhonon-4d813e9773774925bc83d7ac4cd56214)
Energy is the next grand challenge for computing technologies. To meet the computing demands in the AI era, nanoscale logic devices not only need to be scaled in dimensions but also need to lower the switching energy to attojoule ($10^{-18}$ J). To continue this scaling, we are integrating devices with new materials (2D and oxides) and new architectures (Gate-All-Around).
(a) Logic technology moves to GAA structure to continue the scaling in dimension and switching energy. (b) Band tail states (BTS) affecting the electronic energy distribution near conduction band. (c) 2D transistor measurement, compared to silicon technology, as limited by BTS width EU. GAA: gate all around. Transistor structures from Applied Materials, Inc.
Two-dimensional (2D) semiconductors are emerging candidates for nanoscale transistors, because ultrathin 2D channels can reduce short channel effects and have reasonable mobility at sub-nanometer (atomic) thickness. Pushing 2D transistors into commercial adoptions is a pursuit for device community.