Phonons and Valence-band Splitting in Strained GaAs<SUB>1-x</SUB>N<SUB>x</SUB>/GaAs Epilayers

Abstract

The strain effects in strained GaAs<SUB>1-x</SUB>N<SUB>x</SUB> epilayers are characterized by Raman spectroscopy and photocurrent spectra at various nitrogen composition. In addition, the nitrogen composition and the strain were determined by using high-resolution X-ray diffraction (HR-XRD). The Raman spectra are observed to be dominated by the GaAs-like longitudinal optical (LO) phonon mode as the strongest peaks show up around 289~294 cm<SUP>-1</SUP>. Moreover, the weak and broad peaks features in the range of 255~276 cm<SUP>-1</SUP> originate from the peaks of GaAs-like transverse optical (TO) phonon mode and disorder induced, GaN-like LO. And the Raman peak shifts toward lower wave number with increasing nitrogen compositions, which is indicates the presence of tensile strain in the strained GaAs<SUB>1-x</SUB>N<SUB>x</SUB> epilayers. The valence-band splitting of GaAs<SUB>1-x</SUB>N<SUB>x</SUB> are obtained from photocurrent spectra. As the nitrogen concentration increases, the tensile strain in strained GaAs<SUB>1-x</SUB>N<SUB>x</SUB> epilayers increases while the valence-band splitting increases.