Materials World Network: Investigation of Nonpolar and Semipolar GaN on Si and Sapphire: Optical Processes and Efficiency

Virginia Commonwealth University, Richmond VA

Investigators

Abstract

TECHNICAL SUMMARY: The objective of this Materials World Network project is to investigate the fundamentals of nonpolar and semipolar GaN growth on low cost Si and sapphire substrates with the aim of understanding the mechanisms governing defect formation and constituent/impurity incorporation as well as processes responsible for radiative recombination. Insight into mechanisms responsible for the defect formation will make it possible to devise approaches for reducing the defect density, particularly the stacking faults and partial dislocations, and produce high-optical-quality material for light-emitting diodes with enhanced brightness and potentially for laser diodes. The absence of polarization in nonpolar GaN and substantially reduced polarization in semipolar GaN will allow higher recombination efficiencies and eliminate the dependence of emission energy on injection level. After interrogating cleanly the optical matrix elements, In and Mg incorporation, and Mg activation energy in optimized GaN films, systematic studies of oscillator strengths and radiative recombination rates in nonpolar and semipolar InGaN/GaN and GaN/AlGaN quantum wells and double heterostructures will be undertaken to answer the critical question which non-polar and semipolar GaN orientation has the potential to provide higher efficiency light emitters than polar c-plane GaN. NON-TECHNICAL SUMMARY: A multi-institutional/multidisciplinary international program bringing together the unique expertise in growth, available at the Virginia Commonwealth University, extensive capabilities of precise optical measurements at the University of Magdeburg (Germany), and demonstrated experience in theoretical modeling at the University of Montpellier 2 (France) will be undertaken in an effort to understand the synthesis and properties of transformative nonpolar and semipolar nitride semiconductor structures for high efficiency light emitters. This approach will shed the much needed light into the fundamentals of defect formation, impurity incorporation, and optical processes and thus will lay the critical groundwork for attainment of bright light sources for solid-state lighting, as well as lasers and detectors for consumer and military applications. This Materials World Network project will allow a broad perspective of materials science, engineering, and semiconductor theory and provide a fertile ground for teaching graduate and undergraduate students the intricacies of science and soft skills necessary for success in the global, cyber-enabled nanotechnology workforce, with the additional benefit of exposure to cultures of science in the US, Germany, and France. Cross training of graduate students by leading international groups, research experiences for undergraduate students, and expansion of outreach programs for middle school students in the fields of materials science and semiconductor devices will go a long way for training the future skilled workforce. This project is supported by the Electronic and Photonic Materials program and Office of Special Programs, Division of Materials Research.