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

Surface photovoltage (SPV) spectra were measured for GaN _0.014As_0.986 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. © 2014 Elsevier B.V.