Nitrogen induced optical phonon shift in GaNyAs1-y studied by Raman Scattering

Abstract

ABSTRACTWe present a Raman study of pseudomorphically strained epitaxial films of the ternary alloy GaNyAs1-y grown on GaAs(100) with y ranging from 0 to 0.06. The optical phonon Raman spectrum of the alloy displays a two-mode behavior. The GaAs-like first order modes for y = 0.06 are represented by the strong longitudinal optic (LO1) mode at 287.4 cm-1 and the weaker transverse optic (TO1) mode at 269.0 cm-1, while the GaN-like LO2 mode is observed at 475.6 cm-1. Two very broad disorder-induced acoustic bands are evident at 80 and 170 cm-1 due to atomic disorder within the crystalline network. Raman studies show that as the nitrogen concentration in the alloy increases, the GaAs-like LO1 band shifts linearly towards lower wavenumber while the linearly increasing GaN-like LO2 phonon band deviates from linearity at higher nitrogen concentration (y ≥ 0.03). The reason for the deviation of the LO2 phonon from linearity is discussed.