Optical study of the band structure of wurtzite GaP nanowires
S. Assali (Eindhoven University of Technology)
J. Greil (Eindhoven University of Technology)
I. Zardo (Eindhoven University of Technology)
A. Belabbes (Friedrich Schiller University Jena)
M. W.A. De Moor (Eindhoven University of Technology)
Sebastian Koelling (Eindhoven University of Technology)
P. M. Koenraad (Eindhoven University of Technology)
F. Bechstedt (Friedrich Schiller University Jena)
E. P.A.M. Bakkers (TU Delft - QN/Bakkers Lab, Eindhoven University of Technology, Kavli institute of nanoscience Delft)
J. E.M. Haverkort (Eindhoven University of Technology)
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Abstract
We investigated the optical properties of wurtzite (WZ) GaP nanowires by performing photoluminescence (PL) and time-resolved PL measurements in the temperature range from 4 K to 300 K, together with atom probe tomography to identify residual impurities in the nanowires. At low temperature, the WZ GaP luminescence shows donor-acceptor pair emission at 2.115 eV and 2.088 eV, and Burstein-Moss band-filling continuum between 2.180 and 2.253 eV, resulting in a direct band gap above 2.170 eV. Sharp exciton α-β-γ lines are observed at 2.140-2.164-2.252 eV, respectively, showing clear differences in lifetime, presence of phonon replicas, and temperature-dependence. The excitonic nature of those peaks is critically discussed, leading to a direct band gap of ∼2.190 eV and to a resonant state associated with the γ-line ∼80 meV above the Γ8C conduction band edge.
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