Expanding electronics beyond silicon with wide-bandgap, 2D, and ferroelectric materials

This dissertation explores the advancement of microelectronics through novel materials, including two-dimensional (2D) materials, ferroelectric materials, and wide-bandgap semiconductors. These emerging materials enable new functionalities, improve energy efficiency, and enhance stability for various applications. Chapter 1 provides background information for this dissertation, including a brief review of 2D materials, particularly transition metal dichalcogenides (TMDCs). Ferroelectric materials and their device applications are discussed. Additionally, wide-bandgap semiconductors and their advantages are introduced, with a particular focus on gallium nitride (GaN). Chapter 2 explores non-volatile reconfigurable transistors with four-mode operation. Utilizing the strong polarization of epitaxially grown scandium aluminum nitride (ScAlN), a single device can function as an n-type, p-type, always-on, or always-off transistor. The feasibility of these transistors for logic gate applications is demonstrated. Additionally, non-volatile latch operation is presented using van der Waals materials, including ferroelectric copper indium thiophosphate (CIPS) and molybdenum ditelluride (MoTe2). Ferroelectric field-effect transistor (FeFET) with metal-ferroelectric-metal-insulator-semiconductor (MFMIS) structure enables stable memory operation. Using these FeFETs, non-volatile sequential logic operation is demonstrated through a simple latch circuit. Chapter 3 demonstrates the wafer-scale synthesis of MoTe2 using di-tert-butyl telluride ((C4H9)2Te) as the tellurium precursor, along with molybdenum hexacarbonyl (Mo(CO)6) and sputtered molybdenum (Mo) as molybdenum precursors. The successful wafer-scale growth of both 1T' and 2H phases of MoTe2 is presented, with various characterization results confirming the uniformity, phase selectivity, and high crystallinity of the synthesized material. Chapter 4 investigates GaN-based high-electron-mobility transistors (HEMTs) for high-temperature applications. Dielectric stack optimization, gate recess structures, and p-GaN/AlGaN/GaN heterostructures are explored to achieve stable operation up to 500 °C. Optimizing the dielectric stack enhances the breakdown field and device lifetime, while the gate recess and p-GaN/AlGaN/GaN heterostructure enable enhancement-mode operation with improved threshold voltage stability at high temperatures. Chapter 5 concludes this dissertation by summarizing key findings and outlining directions for future research. By integrating emerging materials with innovative design strategies, these studies advance next-generation electronic devices and facilitate their practical implementation in semiconductor technology.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Electrical & Computer Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Lee, Hanwool

Contributors dc:contributor

• Zhu, Wenjuan
• Lyding, Joseph W
• Rakheja, Shaloo
• Zhao, Yang

• 2D Materials
• Ferroelectrics
• Wide-bandgap
• Electronics
• Chemical vapor deposition
• MoTe2
• GaN
• Reconfigurable

Statement dc:rights

• Copyright 2025 Hanwool Lee

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129696

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129696