Abstract
The longitudinal (LO) and transverse (TO) optical Ga–N phonons of thick as-grown Ga1–yInyAs1–xNx/GaAs (001) layers with x~3%–4%, i.e., just above the N-solubility limit xs~2% in GaAs, and y up to 30% are studied by Raman scattering. We observe a three-mode behavior which we associate with Ga–N modes from the isolated Ga4N complexes (~460 cm–1), the Ga3InN ones (~480 cm–1) and the GaN-segregated region (~425 cm–1). The corresponding N fractions are derived via combined contour modeling of the three-mode TO and LO Ga–N Raman lineshapes. We find that substantial In-bonding minimizes GaN segregation only in a very narrow x range of ~1% just above xs.