Evidence of compositional inhomogeneity in InxGa1-xN alloys using ultraviolet and visible Raman spectroscopy.

In this paper we report a study of phase separation in bulk In_xGa_1-xN films grown by metal organic chemical-vapor deposition using mid-UV Raman spectroscopy. Evidence of phase separation is observed by the occurrence of low frequency shoulders identified as minority phase in the A₁(LO) Raman mode. A phase transition in the alloy from the metastable to unstable region was found to be occurring at an indium concentration of about 25%. Raman spectroscopic results also indicate that the compositional inhomogenity in our samples increase, as would be expected, with depth in the film. A direct correspondence is also found between the percentage of indium concentration in the film and the amount of compositional inhomogenity. [ABSTRACT FROM AUTHOR]