Epitaxial Film Growth and Characterization of Stable and Metastable Gallium-Aluminum-Oxide Polymorphs

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

Nontechnical description: Ubiquitous in every-day life, semiconductors are critical components in industrial manufacturing, communications, transportation, energy conversion and transmission, and many other applications. The U.S. CHIPS and Science Act, which provides more than $50 billion to increase domestic research and manufacturing of semiconductors, further highlights the critical importance of semiconductor research to U.S. national security and the economy. This research project creates scientific knowledge to produce a novel semiconductor alloy system and forms a platform for the development and manufacturing of future semiconductor devices that can operate in extreme environments. The capability for semiconductor devices to operate at higher temperatures and higher powers translates to substantial energy savings and more efficient and robust renewable energy technologies, such as long-range electric vehicles. As part of the future workforce, graduate and undergraduate students gain a broad set of skills in new processing methods and advanced characterization tools that are needed in the semiconductor industry. Outreach activities also educate middle/high-school students about semiconductors and related materials to inspire them to consider careers in STEM. The materials and growth recipes resulting from this research advance semiconductor R&D activities: external research groups can produce or acquire semiconductor films through training on the equipment located in Carnegie Mellon University’s clean room user facility, requesting fee-for-service films from clean room staff, or through an established research collaboration with the principal investigator. Technical description: This project is a research investigation on the growth and characterization of different phases, or polymorphs, of gallium-aluminum-oxide (AGO) epitaxial films, which have enormous potential for high-efficiency power-electronic devices that can operate in extreme conditions. The ability to alloy gallium oxide with Al to form different polymorphs of AGO with unique properties and tunable, ultra-wide bandgaps that depend on Al content presents a vast materials system with potential to form a platform for both established and novel semiconductor devices. As such, an ultimate goal of this project is to achieve unprecedented control over the phase content and microstructure of AGO semiconductor epitaxial films. However, the understanding of how to control the growth of one phase versus another in this material system is very limited. Using chemical vapor deposition to produce the films, this research contributes to the understanding of how thermodynamic and kinetic variables can be used to control the growth of stable and metastable polymorphs of AGO as a function of Al content. Prior experimental and theoretical studies serve as points of reference and inform the experimental approach. Advanced materials characterization tools are employed to identify the micro-/ nano-structure, phase content and composition in the films and reveal such phenomena as interdiffusion and phase transitions within the film and at the film/substrate interface, which determine the nature of the resulting film growth. Electrical measurements of films showing optimum structural characteristics uncover properties that are relevant for future electronic devices based on these materials. 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.