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Title: Stark effect in ensembles of polar (0001) Al{sub 0.5}Ga{sub 0.5}N/GaN quantum dots and comparison with semipolar (11−22) ones

This work presents a continuous-wave photoluminescence study of Al{sub 0.5}Ga{sub 0.5}N/GaN quantum dots grown by ammonia-assisted molecular beam epitaxy on sapphire, either on the wurtzite polar (0001) or the semipolar (11−22) plane. Due to interface polarization discontinuities, the polar dots are strongly red-shifted by the Stark effect and emit in the visible range. Carrier injection screening of the polarization charges has been studied. A model relying on average dot heights and dot height variances, as measured by transmission electron microscopy, is proposed. It can account for the injection dependent luminescence energies and efficiencies. The electric field discontinuity deduced from the fittings is in good agreement with theoretical expectations for our barrier composition. On the contrary, semipolar quantum dot ensembles always emit above the gap of GaN strained to Al{sub 0.5}Ga{sub 0.5}N. Their luminescence linewidth is significantly lower than that of polar ones, and their energy does not shift with injection. Our study then confirms the expected strong decrease of the Stark effect for (11−22) grown (Al,Ga)N/GaN heterostructures.
Authors:
; ; ; ; ;  [1] ;  [2] ; ;  [3]
  1. Centre de Recherche sur l'Hétéro-Epitaxie et ses Applications, CNRS, Rue Bernard Grégory, 06560 Valbonne (France)
  2. Laboratoire de Physique de la Matière Condensée, Faculté des Sciences de Tunis, 2092 El Manar (Tunisia)
  3. Department of Physics and KI for the NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 305-701 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22308496
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 3; 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; CARRIERS; ELECTRIC FIELDS; GALLIUM NITRIDES; INJECTION; INTERFACES; MOLECULAR BEAM EPITAXY; PHOTOLUMINESCENCE; POLARIZATION; QUANTUM DOTS; RED SHIFT; SAPPHIRE; SCREENING; STARK EFFECT; STRAINS; TRANSMISSION ELECTRON MICROSCOPY