Optical properties of GaAsNSe/GaAs superlattice investigated by means of piezoelectric photothermal spectroscopy for nonradiative electron transitions

Optical properties of the GaAsNSe/GaAs superlattice (SL) were investigated using piezoelectric photothermal (PPT) and photoluminescence (PL) spectroscopies. The sample was grown by metalorganic molecular beam epitaxy on a semi-insulating (SI-)GaAs substrate. The SL consists of five periods of GaAsNSe and GaAs layers of thickness 11 nm. The temperature variation of the PPT spectrum of this sample was measured down to liquid nitrogen temperature and three peaks were observed at 0.7, 0.90 and 1.25 eV at 80 K. The 1.25 eV peak seems to be due to the bandgap transition of GaAsNSe. Comparing the PPT spectra with the PL results, it was considered that the localised levels caused the PPT signal peaks at 0.7 and 0.90 eV. The intensity of the 0.90 eV peak drastically changed with secondary light illumination. The effect of the electron nonradiative recombination at the interface states should be considered.