Synthesis of Two-Dimensional Oxides via Intercalation through Epitaxial Graphene towards 2D/3D Hot Electron Transistors
Restricted (Penn State Only)
- Author:
- Turker, Furkan
- Graduate Program:
- Materials Science and Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 15, 2024
- Committee Members:
- John Mauro, Program Head/Chair
Rongming Chu, Outside Unit & Field Member
Suzanne Mohney, Major Field Member
Susan Sinnott, Major Field Member
Joshua Robinson, Chair & Dissertation Advisor
Maxwell Wetherington, Major Field Member - Keywords:
- epitaxial graphene
two-dimensional
indium oxide
gallium oxide
intercalation
hot electron transistor
graphene schottky diode - Abstract:
- Combining two and three-dimensional (2D/3D) materials provides a unique route to enabling next-generation hot electron transistors (HETs) ‒ a vertical ballistic device, promising for high-frequency applications since they are not limited by electron velocity saturation or short channel effects. The early demonstrations of HETs suffered from poor material and interface qualities and thick device components (>50 nm). The revival of the HET, with a cut-off predicted frequency above 1 THz, can be correlated with the arrival of 2D materials, such as graphene base and ultrathin tunnel/filter barriers. To achieve terahertz operation in a HET, several fundamental characteristics must first be addressed. These include a high common base current transfer ratio (~100%), current density (103 kA/cm2), common emitter current gain (>100), and a large current saturation potential window. Experimental realization of these features has primarily been hindered by the use of thick and low-quality tunnel or filter barriers. To address this, the work in this dissertation leverages a novel synthesis platform termed confinement heteroepitaxy (CHet) to synthesize 2D gallium oxide (GaOx) and indium oxide (InOx) via two-step intercalation (metal and oxygen) at the epitaxial graphene (EG)/SiC interface to be tested as tunnel/filter barriers in HETs. Through spectroscopy, microscopy, and transport measurements, this work aims to elucidate structural and electronic properties of 2D GaOx and InOx and their efficiency as tunnel or filter barriers in HETs. This dissertation aims to deepen the understanding of HETs by presenting a historical overview and the intercalation technique at the EG/SiC interface in Chapter 1. Chapter 2 will delve into the synthesis and characterization methods for growing 2D oxides and outline the fabrication steps for MOS-based Schottky diodes and HETs. Chapters 3 and 4 are dedicated to the synthesis and characterization of novel 2D GaOx and InOx. Following this, Chapter 5 assesses the performance of HETs employing InOx as either tunnel or filter barrier. The dissertation concludes with Chapter 6, which offers final thoughts and potential research directions.