EAGER: Additive Manufacturing of High-Purity Epitaxial Gallium Nitride

Johns Hopkins University, Baltimore MD

Investigators

Abstract

The printing of single crystal semiconductors is investigated through a unique combination of additive manufacturing and reactive gas phase formation. The localized growth of semiconductors which can form electronic devices would eliminate process steps, saving time, and create unique three-dimensional architectures on a variety of materials platforms. Here liquid metal gallium is locally deposited using a printing technique while being reacted with ammonia to produce gallium nitride, GaN. GaN is an important semiconductor which forms the basis of the solid-state lighting industry and high-power electronic devices. In all device applications, the impurity content can control the materials properties and device characteristics. This EArly-concept Grant for Exploratory Research (EAGER) project will focus on the understanding and developing this reactive printing process with an emphasis on controlling unintentional and intentional impurities. The formation of a new semiconductor printing process would contribute to the national prosperity and open new manufacturing avenues. The educational effort has high school interns from underrepresented groups involved in a hands-on research experience with cutting-edge STEM research on semiconductor synthesis, characterization, and additive manufacturing. Novel techniques for removing oxygen from gallium precursors and mitigating oxygen incorporation into printed gallium nitride will be investigated. Local, epitaxial deposition of the compound semiconductor GaN has been initially demonstrated with the gas-phase reactive additive manufacturing (GRAM) process. The oxygen impurity incorporation in GRAM GaN is an area of concern due to the rapid formation of a native oxide on gallium metal, which is used as the gallium precursor. Several approaches ranging from in situ gas phase as well as wet chemical oxide removal systems are developed and used in combination with detailed characterization to obtain a process understanding of the changes in oxide formation and oxygen incorporation at the growth front. This research will determine the viability of GaN single crystal printing in producing materials of high structural perfection and controlled chemical purity as needed in the device fabrication process. The potential of demonstrating printed GaN with comparable purity that is achievable with standard thin film techniques (i.e. chemical vapor deposition - CVD, hydride vapor phase epitaxy - HVPE) has the potential to revolutionize the way semiconductor device manufacturing is performed. 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.