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Title: Effect of thickness and carrier density on the optical polarization of Al{sub 0.44}Ga{sub 0.56}N/Al{sub 0.55}Ga{sub 0.45}N quantum well layers

The thickness and carrier density of AlGaN quantum well (QW) layers have a strong influence on the valence subband structure, and the resulting optical polarization and light extraction of ultraviolet light-emitting diodes. An ultraviolet-emitting (270–280 nm) multiple quantum well heterostructure consisting of 3 periods of Al{sub 0.44}Ga{sub 0.56}N/Al{sub 0.55}Ga{sub 0.45}N with individual layer thicknesses between 2–3.2 nm is studied both experimentally and theoretically. The optical polarization changes to preferentially polarized perpendicular to the QW plane as the QW thickness increases or the carrier density increases. Calculations show these trends are due to (a) a larger decrease in overlap of conduction band to light and heavy hole envelope functions compared to crystal-field split-off envelope functions, and (b) coupling between the valence subbands where higher heavy hole subbands couple to lower light hole and crystal-field split-off subbands. These changes in the valence band have a profound effect on the optical polarization, emission patterns, and eventual light extraction for ultraviolet emitters at these compositions and thicknesses, and need to be controlled to ensure high device efficiency.
Authors:
; ; ;  [1]
  1. Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)
Publication Date:
OSTI Identifier:
22273479
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 17; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALUMINIUM COMPOUNDS; CARRIER DENSITY; COMPARATIVE EVALUATIONS; CRYSTAL FIELD; ELECTRONIC STRUCTURE; GALLIUM NITRIDES; HETEROJUNCTIONS; HOLES; LAYERS; LIGHT EMITTING DIODES; POLARIZATION; QUANTUM WELLS; THICKNESS; ULTRAVIOLET RADIATION; VALENCE; VISIBLE RADIATION