RAMAN STUDIES OF NITROGEN INCORPORATION IN GAAS1-XNX

We report direct-backscattering Raman studies of GaAs1-xNx alloys, for x less than or equal to 0.03, grown on (001) GaAs. The Raman spectra exhibit a two-mode behavior. The allowed GaAs-like longitudinal-optic phonon near 292 cm(-1) is found to red shift at a rate of -136+/-10 cm (-1)/x. This is well described by the combined effects of strain and a lloying. The GaN-like phonon near 470 cm(-1) is observed to increase i n intensity in direct proportion to x, and to systematically blue shif t at a rate of 197 +/- 10 cm(-1)/x. This blue shift is likewise attrib uted to strain and alloying. The GaAs-like second-order features are a lso seen to broaden slightly and diminish in intensity with increasing nitrogen concentration. These results are attributed to a weak breakd own in the zincblende-crystal long-range order, possibly related to th e presence of ordered domains within the random alloy. (C) 1998 Americ an Institute of Physics. [S0003-6951(98)03735-8].