Growth and Optical Properties of Nonpolar m-Plane GaN on Patterned Si and Sapphire Substrates

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Technical: This project addresses materials science synthesis/processing research of m-plane GaN for use in GaN-based devices. GaN-based materials are higly polar on c-plane which when strain is present or a compositional gradient is introduced resulting in polarization charge. The ensuing Stark shift reduces radiative recombination efficiency and can cause carrier leakage in light emitting diodes (LEDs) reducing their efficiency. The research emphasis will be on synthesis of epitaxial m-plane GaN and investigation of optical processes. An accompanying aim is to explore growth of well-aligned, m-plane GaN films on relatively low cost patterned sapphire and Si substrates to understand the fundamentals of growth mechanisms involved. A basic investigation of non polar m-plane GaN synthesis on inexpensive and readily available, but appropriately patterned substrates will be carried out in conjunction with requisite characterization to gain further understanding on radiative recombination processes in such layers. The orientation and morphology of the films, as well as extended and point defects will be investigated using structural, electrical, and optical characterization techniques. The objective is to explore the science underlying the synthesis of m-plane GaN on low-cost sapphire and Si substrates with etched facets. Additionally, the enhancement of optical matrix elements, p-type conductivity in m-plane oriented epitaxial layers, and basic investigation of quantum confinement effects and their influence on the optical efficiency in the absence of polarization fields will be studied.Non-technical: This project addresses basic research issues in a topical area of materials science with high technological relevance. The research outcomes could pave the way for more efficient light emitters such as LEDs with acceptable color rendering index and efficacy for solid state lighting. These investigations have the potential to produce sufficiently bright light sources for solid state lighting applications, as well as lasers and detectors for consumer and military applications. The research is important in ensuring that the US maintains its current status as a leader in the exploration and implementation of technologies that will lead to energy savings and concomitant environmental benefits. The project also integrates research and education. The PIs have established a collaborative and interdisciplinary research environment for graduate and undergraduate students from electrical engineering and physics fields, and this project will provide graduate and undergraduate students opportunities for valuable cross-disciplinary learning, for interactions with international scientists, for development of industrial connections, in addition to assisting their education and understanding of fundamentals of semiconductor technology and physics. Students are also involved in the PIs' efforts toward reduced green house gas emission by helping to achieve semiconductor based efficient white light generation. Since VCU is a growing urban university with a diverse student body (18% African American, 22% other minorities), the PIs recruit from a relatively large pool of students from underrepresented groups. Consequently, they have established minority students in their laboratories and will continue to address diversity.