Enhancing nanoscale electronics: From novel channels to reconfigurable logic circuits

This dissertation explores advanced semiconductor electronic devices through innovative use of novel channel and dielectric materials, focusing on two-dimensional (2D) transition metal dichalcogenides (TMDCs), ferroelectric materials, and wide-bandgap (WBG) semiconductors, within the framework of the “More than Moore” paradigm. In Chapter 1, an introduction to the challenges and potential of these materials in reconfigurable electronics, optoelectronics and high-power, high-temperature applications is provided, alongside a review of their fundamental properties and significance. Chapter 2 presents reconfigurable transistors based on TMDC heterostructures, such as MoS2/WSe2, which leverage electrostatic gating for dynamic polarity control. By modulating charge injection at the Schottky barrier, these transistors achieve both n-type and p-type operation within a single device. The ambipolar behavior enabled by the heterostructure formation is believed to lay the foundation for the polarity switching of the device. These reconfigurable transistors can serve as promising building blocks for adaptable logic-in-memory systems. Chapter 3 explores non-volatile reconfigurable 4-mode FETs (NVR4M-FETs) incorporating a MoTe2 channel, CuInP2S6 (CIPS) ferroelectric layer, and a multilayer graphene (MLG) floating gate (FG). The combination allows for non-volatile polarity switching via ferroelectric polarization and threshold voltage modulation through the FG. Achieving 14 different logic functions with just two NVR4M-FETs, these devices demonstrate high functional density, highlighting their potential in in-memory computing and secure circuit applications. In Chapter 4, the chemical vapor deposition (CVD) synthesis of monolayer ternary TMDC tellurides, specifically WSe2-2xTe2x, was explored to develop materials with tunable optical bandgaps. The study demonstrated gradual bandgap modulation across single flakes and showed unique electronic and optoelectronic properties promising for optoelectronic applications. High-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) characterization confirmed the spatial modulation of the Te concentration, which was consistent with the trend observed from photoluminescence (PL) measurements and density functional theory (DFT) calculations. Chapter 5 addresses gate dielectric stack engineering to achieve thermal stability in 4H-SiC metal-insulator-semiconductor field-effect transistors (MISFETs). A tri-layer dielectric stack of SiO2, SiNx, and Al2O3 was developed to achieve reliable device operation at 500°C. The 4H-SiC MISFETs based on this SiO2/SiNx/Al2O3 gate dielectric stack achieved a field-effect mobility of 39.4 cm2/V·s, a low off-state current of 3.6×10−9 mA/mm, and an exceptional on/off ratio of 109 at 500 ℃. The low interface trap density (1.3× 1011 cm-2eV-1 at E – EV = 0.2 eV at room temperature) confirmed the excellent interface quality between the gate dielectric stack and 4H-SiC. These results underscore the effectiveness of this dielectric stack in maintaining device performance under extreme conditions. Chapter 6 concludes the thesis, discussing the potential of these materials and device architectures for next-generation electronics. Suggested directions include advancing reconfigurable transistor designs to balance high on-current with non-volatility, refining CVD growth parameters for TMDC uniformity, and optimizing SiC interface quality for enhanced MISFET mobility. Overall, this thesis contributes to the field by developing novel material systems and device configurations that address key limitations in current semiconductor technology, advancing applications in fields such as high-temperature electronics, logic-in-memory energy-efficient computing devices and systems that aligned with the “More than Moore” objectives.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Electrical & Computer Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2024

Author dc:creator

• Kang, Junzhe

Contributors dc:contributor

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

• Semiconductor
• Electronic Device
• 2d Materials
• Wide-bandgap Semiconductors

Statement dc:rights

• Copyright 2024 Junzhe Kang

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/127398

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F127398