Investigation of Built-in Electric Fields at the GaSe/GaAs Interface by Photoreflectance Spectroscopy

Built-in electric fields appear during the molecular-beam epitaxy of GaSe on a GaAs(001) substrate at the GaSe/GaAs interface, the presence of the fields is evidenced by Franz–Keldysh oscillations observed in photoreflectance spectra. The varying values of the strength of these fields (from 9.8 to 17.6 kV/cm) can be associated both with the diffusion of Se atoms into the GaAs substrate (buffer layer) and with the formation of transient submonolayers during epitaxial growth. Built-in fields are not observed at the interface of structures grown on GaAs(111)B and GaAs(112) substrates, which can be explained by the lower propagation efficiency of Se into the substrate with mentioned orientations when compared with GaAs(001).