Nitrogen incorporation in GaInNAs and GaAsN near the solubility limit

The influence of nitrogen incorporation on the microstructure of GaAsN/GaAs and GaInNAs/GaAs has been investigated using cross-sectional scanning transmission electron microscopy and laser Raman spectroscopy. Energy-dispersive X-ray maps of the elemental distributions of Ga, In, N and As show that for GaAsN and GaInNAs layers containing nitrogen below the solubility limit, homogeneous compositions are obtained. These layers are of good crystalline quality near to the epilayer/GaAs interface. For GaAsN specimens with nitrogen contents above the solubility limit a graded transition from arsenide-like to nitride-like material occurs after some 50 nm of growth. This observation complements Raman spectra that show that characteristic GaN-like modes are observed in the high nitrogen content GaAsN film. The GaInNAs film containing nitrogen above the solubility limit shows a cellular microstructure consisting of gallium-depleted InGaAs cells with cell wells of a GaN-like composition.