Optical properties of strained wurtzite gallium phosphide nanowires
J. Greil (Eindhoven University of Technology)
S. Assali (Eindhoven University of Technology)
Y. Isono (Kobe University)
A. Belabbes (King Abdullah University of Science and Technology, Friedrich Schiller University Jena)
F. Bechstedt (Friedrich Schiller University Jena)
F. O. Valega MacKenzie (TNO)
A. Yu Silov (Eindhoven University of Technology)
E. P.A.M. Bakkers (Eindhoven University of Technology, Kavli institute of nanoscience Delft, TU Delft - QN/Bakkers Lab)
J.E.M. Haverkort (Eindhoven University of Technology)
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Abstract
Wurtzite gallium phosphide (WZ GaP) has been predicted to exhibit a direct bandgap in the green spectral range. Optical transitions, however, are only weakly allowed by the symmetry of the bands. While efficient luminescence has been experimentally shown, the nature of the transitions is not yet clear. Here we apply tensile strain up to 6% and investigate the evolution of the photoluminescence (PL) spectrum of WZ GaP nanowires (NWs). The pressure and polarization dependence of the emission together with a theoretical analysis of strain effects is employed to establish the nature and symmetry of the transitions. We identify the emission lines to be related to localized states with significant admixture of Δ7c symmetry and not exclusively related to the Δ8c conduction band minimum (CBM). The results emphasize the importance of strongly bound state-related emission in the pseudodirect semiconductor WZ GaP and contribute significantly to the understanding of the optoelectronic properties of this novel material.
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