Raman Characterization of Strained GaN_yAs_(1-y) and In_xGa_(1-x)N_yAs_(1-y) Epilayers

摘要

Pseudomorphically strained epitaxial films of the ternary alloy GaN_yAs_(1-y) have been grown on GaAs(100) with y ranging from 0 to 0.05. The optical phonon Raman spectrum of the alloy displays a two-mode behavior. The GaAs-like first order modes are represented at y = 0.05 by the strong longitudinal optic (LO_1) mode at 288.5 cm~(-1) and the weaker transverse optic (TO_1) mode at 268.3 cm~(-1), while the GaN-like LO_2 mode is observed at 474.8 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 increases, the GaAs-like LO_1 band shifts linearly towards lower wavenumber while the GaN-like LO_2 phonon band displays a sub-linear increase in wavenumber. Raman results for the unstrained quaternary alloy In_(0..06)Ga_(0.94)N_(0.02)As_(0.98) are compared with those of GaN_(0.02)As_(0.98).