Investigation of built-in electric fields at the GaSe/GaAs interface by photoreflectance spectroscopy

The built-in electric fields are generated at the GaSe/GaAs heterointerface when GaSe layers are grown by molecular beam epitaxy on GaAs(001) substrates. The existence of these fields is indicated by the clearly observed Franz–Keldysh oscillations in the photoreflectance spectra. The different values of the intensities of these fields (within the 9.8–17.6 kV/cm range) can be associated both with the diffusion of Se atoms into the GaAs substrate (or into the GaAs buffer layer) and the formation of transition sub-monolayers at initial growth stages. No built-in fields were observed at the GaSe/GaAs heterointerface in case of GaSe layers grown on GaAs(111)B and GaAs(112) substrates, which can be explained by the lower efficiency of Se penetration into these substrates in contrast to GaAs(001).