Polarization dependent photocurrent spectroscopy of single wurtzite GaAs/AlGaAs core-shell nanowires

The optoelectronic properties of single wurtzite GaAs/AlGaAs core-shell nanowires with electrical contacts to the GaAs core are investigated by polarization dependent photocurrent spectroscopy. It is shown that the optical selection rules of the wurtzite GaAs band structure play a major role in observed reversals of the polarization anisotropy in photocurrent as the excitation laser energy changes. The general features of the polarization dependent photocurrent spectra are explained by considering additional effects such as the nanowire dielectric mismatch, Urbach tail, and Franz-Keldysh effect. The optical selection rules allow us to estimate the heavy-hole/light-hole splitting to be ∼90 meV in wurtzite GaAs.