title: An AlGaN Core-Shell Tunnel Junction Nanowire Light-Emitting Diode Operating in the Ultraviolet-C Band.
abstract: To date, semiconductor light emitting diodes (LEDs) operating in the deep ultraviolet (UV) spectral range exhibit very low efficiency due to the presence of large densities of defects and extremely inefficient p-type conduction of conventional AlGaN quantum well heterostructures. We have demonstrated that such critical issues can be potentially addressed by using nearly defect-free AlGaN tunnel junction core-shell nanowire heterostructures. The core-shell nanowire arrays exhibit high photoluminescence efficiency (∼80%) in the UV-C band at room temperature. With the incorporation of an epitaxial Al tunnel junction, the p-(Al)GaN contact-free nanowire deep UV LEDs showed nearly one order of magnitude reduction in the device resistance, compared to the conventional nanowire p-i-n device. The unpackaged Al tunnel junction deep UV LEDs exhibit an output power >8 mW and a peak external quantum efficiency ∼0.4%, which are nearly one to two orders of magnitude higher than previously reported AlGaN nanowire devices. Detailed studies further suggest that the maximum achievable efficiency is limited by electron overflow and poor light extraction efficiency due to the TM polarized emission.
authors.affiliation: Department of Electrical and Computer Engineering, McGill University , 3480 University Street, Montreal, Quebec H3A 0E9, Canada.
authors.forename: S M
authors.initials: SM
authors.lastname: Sadaf
authors.affiliation: Department of Electrical and Computer Engineering, McGill University , 3480 University Street, Montreal, Quebec H3A 0E9, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Zhao
authors.affiliation: Department of Electrical and Computer Engineering, McGill University , 3480 University Street, Montreal, Quebec H3A 0E9, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Electrical and Computer Engineering, McGill University , 3480 University Street, Montreal, Quebec H3A 0E9, Canada.
authors.forename: Y-H
authors.identifier: 0000-0002-3303-136X
authors.initials: YH
authors.lastname: Ra
authors.affiliation: Department of Electrical and Computer Engineering, McGill University , 3480 University Street, Montreal, Quebec H3A 0E9, Canada.
authors.forename: X
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Electrical and Computer Engineering, McGill University , 3480 University Street, Montreal, Quebec H3A 0E9, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Vanka
authors.affiliation: Department of Electrical Engineering and Computer Science, Center for Photonics and Multiscale Nanomaterials, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Z
authors.initials: Z
authors.lastname: Mi
keywords: AlGaN; Nanowire; core−shell; light-emitting diode; molecular beam epitaxy; tunnel junction