Determination of the band gap and the split-off band in wurtzite GaAs using Raman and photoluminescence excitation spectroscopy

GaAs nanowires with 100% wurtzite structure are synthesized by the vapor-liquid-solid method in a molecular beam epitaxy system, using gold as a catalyst. We use resonant Raman spectroscopy and photoluminescence to determine the position of the crystal-field split-off band of hexagonal wurtzite GaAs. The temperature dependence of this transition enables us to extract the value at 0 K, which is 1.982 eV. Our photoluminescence excitation spectroscopy measurements are consistent with a band gap of wurtzite GaAs below 1.523 eV.