Berlin 2001 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 17: Poster: Spectroscopy and Single Particle Spectroscopy of Molecular Systems, Photoprocesses, Biological Systems
CPP 17.11: Poster
Tuesday, April 3, 2001, 12:30–15:00, AT1
Polytype Distribution and Franz-Keldysh Effect in Gallium Selenide as Investigated with Confocal Luminescence Microscopy — •L. Kador1, Y. Fan1, K. Allakhverdiev2, and E. Yu. Salaev3 — 1University of Bayreuth, Institute of Physics and Bayreuther Institut für Makromolekülforschung (BIMF), D–95440 Bayreuth — 2Marmara Research Centre of TÜBITAK, Materials and Chem. Technol. Research Institute, P. K. 21, TR–41470 Gebze/Kocaeli — 3Institute of Photoelectronics, Azerbaijan Academy of Sciences, Baku, Azerbaijan
Gallium selenide (GaSe) is a layered semiconductor with a band gap in the visible spectral region (≈ 620 nm) and high nonlinear optical susceptibility χ(2). Single crystals of GaSe were investigated with a confocal Raman / luminescence microscope operating with a HeNe laser. Strong photoluminescence bands were found to the blue of the excitation wavelength, which are interpreted as luminescence from indirect-gap excitons preceded by second-harmonic generation in the tight laser focus. The photoluminescence spectrum shows three distinct peaks, which are ascribed to different crystal modifications (or polytypes) of GaSe. Spatial scanning of the crystal with respect to the laser focus yields an image of the distribution of the three polytypes. In strong electric fields, the bands exhibit a red shift due to the Franz-Keldysh effect.