ERI: LPCVD-Based Growth and Etching of Gallium Oxide for High Aspect Ratio Vertical Trench Schottky Barrier Diodes

Abstract Title: ERI: Low Pressure CVD-Based Growth and Etching of Gallium Oxide for High Aspect Ratio Vertical Trench Schottky Barrier Diodes
Abstract:
As electricity demand continues to grow across diverse sectors including electric transportation, smart grids, renewable energy, aerospace, industrial automation, and data-intensive computing, the need for efficient, compact, and reliable power management has become increasingly critical. Electricity is emerging as the dominant form of energy consumption, and by 2030, nearly 80 percent of all electric power in the U.S. is expected to pass through power electronic devices. These systems regulate how energy is generated, transmitted, and consumed, making their efficiency and reliability vital to national infrastructure. However, today’s power electronics rely largely on silicon-based devices, which are now approaching their physical and thermal performance limits. These limitations result in significant energy losses and restrict the scalability of power systems in high-demand applications. While commercial adoption of wide bandgap materials such as silicon carbide and gallium nitride has enabled performance gains in select applications, transformative improvements are still needed to realize their full potential at scale. Among these, beta gallium oxide (beta-Ga₂O₃) offers superior voltage handling capability than existing wide bandgap semiconductors, enabling smaller, lighter, and more energy-efficient high-power devices. Despite its promise, key challenges remain in synthesizing high-quality material, processing it without damage, and translating it into functional, high-voltage devices. This project will address these challenges by advancing the materials and processing foundations necessary to enable the next generation of high-voltage diodes. This research spans the full development pipeline, from high-quality materials synthesis to damage-free processing and fabrication of multi-kilovolt class power diodes optimized for low-loss and high-voltage operation, addressing a critical need for compact, robust, and scalable components in future power systems. Additionally, the project will provide hands-on research experiences for undergraduate and graduate students, helping to build technical expertise in semiconductor processing and support national efforts to expand the domestic microelectronics workforce.

The goal of this project is to build a foundational understanding of gallium oxide material synthesis, processing, and device-level integration to enable high-voltage power diode applications. The project centers on three key, interconnected goals. First, the project will establish a scalable low-pressure chemical vapor deposition (LPCVD) growth platform optimized for high growth rates and excellent crystal quality to enable the development of thick, lightly Si-doped beta-Ga₂O₃ drift layers with high electron mobility, ultra-low background carrier concentration, and minimal compensation. Second, it will introduce an in-situ, plasma-damage free, and anisotropic etching method using solid-source metallic gallium within the LPCVD environment to fabricate high-aspect-ratio vertical trench structures. This approach leverages crystallographic orientation-dependent etch behavior to achieve smooth sidewalls and pristine etched surfaces, enabling the fabrication of complex 3D structures including trenches, fins, and nanopillars. Directional dependence of fin orientation, substrate crystallography, and their impact on etch rate, surface morphology, and dopant segregation will also be investigated. Third, vertical trench Schottky barrier diodes will be fabricated and evaluated, integrating the optimized grown and etched materials to demonstrate high device-level performance, including high breakdown voltage, low on-resistance and minimal leakage, and to validate the effectiveness of the underlying material and process innovations. Comprehensive structural, electrical, and surface characterizations will be performed to systematically correlate growth and etching process conditions with material properties and device performance. The project's intellectual significance extends to advancing fundamental understanding of carrier generation and mass transport, doping behavior, and etch chemistry in beta-Ga₂O₃, while also demonstrating a scalable path to ultra-wide bandgap power diodes that meet the stringent requirements of future high-voltage, high-efficiency power electronics systems.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Award Number: 2501623
Principal Investigator: Anhar Bhuiyan
Funds Obligated: $200,000
State: MA