Structure of GaAsN alloy within miscibility gap

We report on the structural and electronic properties of a series of GaAs1-xNx with wide x range. The alloys were grown on (001) GaAs substrate using plasma-assisted molecular beam epitaxy. Transmission electron microscopy and selective area electron diffraction (SAD) were used to probe the crystalline of GaAs0.496N0.504 sample. The results indicate that the alloy is polycrystalline and amorphous. In the polycrystalline observed zinc-blende (ZB) and hexagonal structure. In this result, we suggest generation of miscibility and phase separation from two kind of structure. Calculation the vertical and horizontal lattice constant with x in the range from 0.106-0.848. Observed the az is dramatic drop with increase N content and axy slow decrease, we suggest this result relation of nitrogen cluster alone [001] and residual horizontal substrate strain. Photo-modulated reflectance spectroscopy was used to determine the energy gap of the GaAs1-xNx alloys, which ranges from 0.7-2.0 eV, covering a large part of the solar spectrum. The energy gap is in agreement with BAC model.