N-induced vibrational modes in GaAsN and GaInAsN studied by resonant Ramanscattering

Vibrational modes introduced by the incorporation of N into GaAs and GaInAs have been studied by Raman spectroscopy on samples grown by molecular-beam epitaxy using a rf nitrogen plasma source. When proceeding from GaAs1-xNx to Ga1-yInyAs1-xNx with x less than or equal to0.04 and y less than or equa l to0.12, the nitrogen-induced vibrational mode near 470 cm-1 observed in G aAsN was found to broaden and to split into up to three components with one component at a frequency higher than that of the Ga-N mode in GaAsN. This observation shows that the incorporation of In into GaAsN strongly affects the local bonding of the N atoms by changing the local strain distributions as well as the formation of a significant fraction of In-N bonds. The reso nant enhancement in the scattering cross section of the Ga-N vibrational mo de, observed in low N-content GaAs1-xNx (x approximate to0.01) for incident photon energies matching the mostly N-related E+ transition at around 1.8 eV, was found to broaden significantly upon increasing N content as well as upon the addition of In to form GaInAsN. (C) 2001 American Institute of Ph ysics.