Collaborative Research: Fundamental Studies of the Properties of B-III-N Wide-Bandgap Semiconductor Alloys

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Non-technical Description: This collaborative research project studies an underexplored semiconductor materials system that involves boron incorporation in the four-element alloys of BAlGaN. These materials are a new generation of III-V alloy system compared to the AlInGaN alloys that have been developed to provide high-efficiency lighting. The solid-state illumination and lighting technology, based upon AlInGaN alloys, has found wide practical applications in automotive, liquid-crystal-display back panel, mobile communications and signage illumination, and will soon dominate in general lighting. However, there are still important limitations for AlInGaN alloy materials. This research project explores the advantages of incorporation of boron into these alloys with the ultimate goal to achieve better strain matching in heterostructures, higher efficiency and potentially p-type doping in the new alloy system. The research is integrated with the educational activities including research training for graduate and undergraduate students in the growth, characterization, and processing of these novel materials, and various outreach programs at both Georgia Institute of Technology and Arizona State University.Technical Description: The primary focus of this research project is to study the physical, chemical, and electronic properties of high-quality thin films of boron-containing III-nitride semiconductor ternary and quaternary alloys in the technologically important range of compositions and to develop an in-depth understanding of fundamental materials science for improved optoelectronic device designs. The research team uses advanced metalorganic chemical vapor deposition (MOCVD) epitaxial film growth systems, and performs in-depth studies of the effects of growth conditions, substrate materials, substrate orientation, and doping. The materials properties are studied in detail using state-of-the-art nanoscale characterization tools: the crystal structure is studied using atomic-resolution aberration-corrected transmission electron microscopy; the electronic band structure is determined by electron holography; and the optical properties are measured by cathodoluminescence with high spatial- and temporal-resolution. Exploring the effects of compositional homogeneity, phase separation, and piezoelectric fields is also included in the research. The microstructural properties are correlated with the optoelectronic properties to understand the role of growth parameters on overall device performance.