Diamond power electronics for the next generation electric grid

The escalating electricity demands of transportation and artificial intelligence, coupled with the urgent imperative to mitigate global warming, require transformative advancements in the electric grid. Achieving net-zero emissions hinges on the rapid integration of renewable energy sources like solar and wind, where power electronics play a central role in enabling efficient energy conversion, resilient distribution, and real-time grid stabilization. These systems must also withstand disruptions from extreme weather, cyber-physical threats, and outages, necessitating devices with unprecedented speed, efficiency, and reliability. This thesis delves into the potential of diamond as an ultrawide-bandgap semiconductor in revolutionizing power devices for the future electric grid. Diamond's exceptional properties, including its large bandgap (5.47 eV), high critical electric field (10 – 20 MV/cm), high carrier mobility (up to 2100 cm²/V/s), and superior thermal conductivity (22 - 24 W/cm/K)—enable devices that surpass the limitations of silicon, silicon carbide (SiC), and gallium nitride (GaN). The research advances diamond-based technologies through three key innovations: First, the development of essential fabrication and processing techniques, including the formation of ohmic and Schottky contacts on oxygen-terminated diamond surfaces and the ICP-RIE process, is introduced. Based on these techniques, the experimental demonstration of high breakdown voltage (> 4.6 kV) diamond lateral Schottky barrier diodes (SBDs) is presented. This demonstration is thanks to the innovative lateral architecture with a contact layer selective regrowth approach and field-plate edge termination technique. Al2O3 field plates mitigate the electric field crowding near the edge of the contacts and improve reverse bias performance. The SBDs with the Al2O3 field plate exhibit a leakage current density lower than 0.01 mA/mm under a reverse bias of 4.6 kV, marking one of the highest breakdown voltages ever reported by diamond SBDs. This is also the first report of lateral diamond SBDs with the field-plate edge termination technique. Second, fundamental studies on diamond photoconductive semiconductor switches (PCSS) are conducted. A controlled comparative analysis reveals that low impurity concentrations in type IIa diamond substrates are critical for optimal performance. Large-area, wafer-scale lateral diamond PCSS on commercial substrates are validated, demonstrating bidirectional switching at ±1.2 kV, 8.0 A on-state current, and an on/off ratio of 2.3×10¹¹ under intrinsic 218 nm laser triggering. These results establish a clear pathway for diamond PCSS to outperform SiC/GaN in high-power, high-speed grid applications. Finally, to achieve a breakthrough in diamond PCSS performance, a novel lateral PCSS design is proposed, eliminating the half-century-old tradeoff between power handling and speed in traditional PCSS. By integrating a buried metallic p+ current channel and impurity-free diamond, this buried channel design achieves a record current density (i.e., 44 A/cm under low DC bias of 60 V), large on/off ratios (>1011), and fast rise and fall times (~2 ns). The design, fabrication, modeling, and characterization of this new buried channel PCSS prototype are presented for the first time. This study overcomes critical limitations of conventional PCSS, which either rely on low-critical-field semiconductors (e.g., Si, GaAs), destructive current filamentation, or sub-bandgap laser triggering—factors that restrict device scalability and reliability in grid-scale applications. By presenting key fabrication techniques, device optimization and scaling, and novel device architectures, this work positions diamond power devices as building blocks for future resilient, efficient, and sustainable power grids.

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

• Han, Zhuoran

Contributors dc:contributor

• Bayram, Can
• Dallesasse, John
• Goddard, Lynford
• Pernot, Julien
• Stillwell, Andrew

• diamond
• power electronics
• semiconductors
• photoconductivity
• Schottky barrier diodes
• transistors

Statement dc:rights

• Copyright 2025 Zhuoran Han

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129702

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129702