Photoreflectance Study on the Interface of InGaP/GaAs Heterostructures Grown by Gas Source Molecular Beam Epitaxy

The photoreflectance spectra of an undoped InGaP film grown on a GaAs (001) substrate by gas-source molecular beam epitaxy have been measured at the temperature of 70 K. The band-gap optical transitions attributed to the InGaP epilayer and GaAs substrate have been characterized. Two broad features, which originate from the interface of the InGaP and GaAs layer, also appeared with the transition energies of 1.523 eV and 1.877 eV in the photoreflectance spectra. In addition, the amplitudes of these two optical features show different trends with increasing power of an extra DC pumping laser. The results suggest that the two unusual optical features are attributed to the spatial indirect transitions at the interface.