Thermal transport in two-dimensional and wide band gap materials
Abstract/Contents
- Abstract
- The semiconductor industry has seen much interest in materials beyond silicon. Among these, two-dimensional (2D) nanomaterials are known to exhibit distinct evolution of chemical and physical properties as the material thickness is scaled from bulk to atomic layers. Wide band gap (WBG) materials have also attracted attention due to their promising applications in power electronics and short wavelength photonics. This work begins by summarizing the thermal properties of 2D materials, including thermal conductivity, thermal boundary conductance, and thermoelectric properties. We then study thermal and electrical transport in WTe2, which is a semimetallic 2D material. Thermal properties of WTe2 devices are extracted from the device electrical characteristics using an analytical model. We also use finite element simulations to estimate the current density improvements by novel heat dissipation structures, including capping layers such as hexagonal boron nitride (h-BN). This work demonstrates that WTe2 can carry high current density despite its low thermal conductivity, which shows its potential applications as a thermal barrier or electrode in phase-change memory. Next, we discuss thermal conductivity of crystalline AlN and the influence of atomic-scale defects. AlN plays a key role in modern power electronics and deep-ultraviolet photonics. In these devices, heat dissipation is important during high-power and high-temperature operation. Using the 3ω characterization method, we measure temperature dependent thermal conductivity of AlN single crystals, between 100 and 400 K. Experimental data are compared with analytical models. We also investigate size effects and accumulated thermal conductivity of AlN thin films, which are widely used as buffer layer or capping layer in power electronic devices or light-emitting diodes. This work improves the understanding of AlN thermal conductivity and demonstrates how this material influences heat dissipation in wide band gap devices. We also study the temperature reduction of GaN devices with polycrystalline diamond top capping layer by Raman thermometry. Experimental results are compared with an analytical model and finite element simulations. These results provide a fundamental understanding of how to improve heat dissipation in GaN transistors. Combined, these studies shed light into the fundamental thermal properties of 2D and WBG materials. In addition, these results also serve as the foundations to design 2D and WBG devices and systems with better heat dissipation capabilities
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2020; ©2020 |
| Publication date | 2020; 2020 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Xu, Runjie |
|---|---|
| Degree supervisor | Pop, Eric |
| Thesis advisor | Pop, Eric |
| Thesis advisor | Chowdhury, Srabanti |
| Thesis advisor | Saraswat, Krishna |
| Degree committee member | Chowdhury, Srabanti |
| Degree committee member | Saraswat, Krishna |
| Associated with | Stanford University, Department of Electrical Engineering |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Runjie (Lily) Xu |
|---|---|
| Note | Submitted to the Department of Electrical Engineering |
| Thesis | Thesis Ph.D. Stanford University 2020 |
| Location | https://purl.stanford.edu/sj080yf2289 |
Access conditions
- Copyright
- © 2020 by Runjie Xu
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
Also listed in
Loading usage metrics...