Compositional Ordering in InxGa1-xN and its influence on optical properties (original) (raw)

ABSTRACTInxGa1-x N layers grown with compositions with the predicted miscibility gap have been studied using Transmission Electron Microscopy (TEM), x-ray diffraction and optical measurements (photoluminescence and absorption). The samples (0.34 < × < 0.8) were deposited by Molecular Beam Epitaxy at 800°C using 200 nm AlN buffer layer grown directly on sapphire substrates. Another sample with × = 0.34 was grown on a GaN buffer layer. Dislocation densities in the InGaN layers were typically in the mid-1010 cm−2 to1011 cm−2 range. Edge dislocations were the most prevalent. For In concentration × = 0.5 compositional ordering is observed leading to extra diffraction spots in electron and x-ray diffraction. The ordering was not observed for the sample with x=0.34 grown on GaN. Based on TEM measurements the estimated period of ordering Δ was about Δ = 45 Å for × = 0.5 and Δ = 65Å for × = 0.78. The sample with × = 0.5 had the highest dislocation density. In addition to the presence o...