title: AgGaSe2 thin films grown by chemical close-spaced vapor transport for photovoltaic applications: structural, compositional and optical properties.
abstract: Thin films of chalcopyrite AgGaSe(2) have been successfully grown on glass and glass/molybdenum substrates using the technique of chemical close-spaced vapor transport. The high crystallinity of the samples is confirmed by grazing-incidence x-ray diffraction, scanning and transmission electron microscopy, and optical transmission/reflection spectroscopy. Here, two of the three expected direct optical bandgaps are found at 1.77(2) and 1.88(6) eV at 300 K. The lowest bandgap energy at 4 K is estimated to be 1.82(3) eV. Photoluminescence spectroscopy has further revealed the nature of the point defects within the AgGaSe(2), showing evidence for the existence of very shallow acceptor levels of 5(1) and 10(1) meV, and thus suggesting the AgGaSe(2) phase itself to exhibit a p-type conductivity. At the same time, electrical characterization by Hall, Seebeck and four-point-probe measurements indicate properties of a compensated semiconductor. The electrical properties of the investigated thin films are mainly influenced by the presence of Ag(2)Se and Ga(2)O(3) nanometer-scaled surface layers, as well as by Ag(2)Se inclusions in the bulk and Ag clusters at the layers' rear side.
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institute for Heterogeneous Material Systems, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany. christoph.merschjann@helmholtz-berlin.de
authors.forename: C
authors.initials: C
authors.lastname: Merschjann
authors.forename: M
authors.initials: M
authors.lastname: Mews
authors.forename: T
authors.initials: T
authors.lastname: Mete
authors.forename: A
authors.initials: A
authors.lastname: Karkatzinou
authors.forename: M
authors.initials: M
authors.lastname: Rusu
authors.forename: B V
authors.initials: BV
authors.lastname: Korzun
authors.forename: S
authors.initials: S
authors.lastname: Schorr
authors.forename: P
authors.initials: P
authors.lastname: Schubert-Bischoff
authors.forename: S
authors.initials: S
authors.lastname: Seeger
authors.forename: Th
authors.initials: T
authors.lastname: Schedel-Niedrig
authors.forename: M-Ch
authors.initials: MC
authors.lastname: Lux-Steiner
mesh_terms: D004553:Electric Conductivity; D004563:Electrochemistry / Q000379:methods; D005708:Gallium / Q000737:chemistry*; D049449:Luminescence; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning / Q000379:methods; D046529:Microscopy, Electron, Transmission / Q000379:methods; D008968:Molecular Conformation; D036103:Nanotechnology / Q000379:methods; D055095:Optics and Photonics; D010777:Photochemistry / Q000379:methods; D012643:Selenium / Q000737:chemistry*; D012666:Semiconductors; D012834:Silver / Q000737:chemistry*; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D012834:Silver; D005708:Gallium; D012643:Selenium