Deep level electronic structure of ZnSe/GaAs heterostructures |
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Authors: | A Raisanen L J Brillson A Franciosi R Nicolini L Vanzetti L Sorba |
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Affiliation: | (1) Xerox Webster Research Center, 800 Phillips Road 0114-41D, 14580 Webster, NY;(2) Area di Ricerca, Laboratorio Tecnologie Avanzate Superfici e Catalisi dell’ Istituto Nazionale di Fisica della Materia, Padriciano 99, 1-34012 Trieste, Italy;(3) Department of Chemical Engineering and Materials Science, University of Minnesota, 55455 Minneapolis, MN |
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Abstract: | We performed 1—2 keVcathodoluminescence measurements and He-Ne and HeCd excited photoluminescence studies of ZnSe/GaAs( 100)
heterostructures grown by molecular beam epitaxy. Our goal was to investigate the deep level electronic structure and its
connection with the heterojunction band offsets. We observed novel deep level emission features at 0.8, 0.98, 1.14, and 1.3
eV which are characteristic of the ZnSe overlayer and independent in energy of overlayer thickness. The corresponding deep
levels lie far below those of the near-bandedge features commonly used to characterize the ZnSe crystal quality. The relative
intensity and spatial distribution of the deep level emission was found to be strongly affected by the Zn/Se atomic flux ratio
employed during ZnSe growth. The same flux ratio has been shown to influence both the quality of the ZnSe overlayer and the
band offset in ZnSe/GaAs heterojunctions. In heterostructures fabricated in Se-rich growth conditions, that minimize the valence
band offset and the concentration of Se vacancies, the dominant deep level emission is at 1.3 eV. For heterostructures fabricated
in Zn-rich growth conditions, emission by multiple levels at 0.88,0.98, and 1.14 eV dominates. The spectral energies and intensities
of deep level transitions reported here provide a characteristic indicator of ZnSe epilayer stoichiometry and near-interface
defect densities. |
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Keywords: | Cathodoluminescence (CL) deep levels heterojunction interface molecular beam epitaxy (MBE) photoluminescence (PL) znSe/GaAs |
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