Surface photovoltage and modulation spectroscopy of E− and E+ transitions in GaNAs layers

• The E+ transition in GaNAs has been observed in surface photovoltage (SPV) spectroscopy.
• The E− transition was observed in SPV spectra besides the E+ transition.
• The same optical transitions were observed in photoreflectance and contactless electroreflectance spectra.
• Energies of E− and E− transitions were explained within the band anticrossing model.
• We showed that SPV spectroscopy is a good technique to study dilute nitrides.

Surface photovoltage (SPV) spectra were measured for GaN0.014As0.986 layers at room temperature and compared with room temperature photoreflectance (PR) and contactless electroreflectance (CER) measurements. Spectral features related to E− and E+ transitions were clearly observed in SPV spectra at energies corresponding to PR and CER resonances. In this way it has been shown that SPV spectroscopy is an alternative absorption-like technique to study both the E− and E+ transitions in dilute nitrides. The observation of E+ transition in SPV spectra means that it is a direct optical transition at the Γ point of GaNAs band structure which can be explained by the band anticrossing interaction between the localized states of N and the extended conduction band states of the GaAs host.