Influence of InN and AlN concentration on the compositional inhomogeneity and formation of InN-rich regions in InxAlyGa1−x−yN

Kusch, Gunnar and Enslin, Johannes and Spasevski, Lucia and Teke, Tolga and Wernicke, Tim and Edwards, Paul R. and Kneissl, Michael and Martin, Robert W. (2019) Influence of InN and AlN concentration on the compositional inhomogeneity and formation of InN-rich regions in InxAlyGa1−x−yN. Japanese Journal of Applied Physics, 58 (SC). SCCB18. ISSN 0021-4922

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    Abstract

    The application of quaternary InxAlyGa1−x−yN active regions is a promising path towards high efficiency UVB-LEDs. For the utilisation of InxAlyGa1−x−yN, detailed knowledge of the interplay between growth parameters, adatom incorporation, optical and structural properties is crucial. We investigated the influence of the TMAl and TMIn flux on the composition and luminescence properties of InxAlyGa1−x−yN layers by multi-mode scanning electron microscopy. We found that varying the molar TMIn flow from 0 to 17.3 µmol/min led to an InN concentration between 0% and 3.2% and an emission energy between 4.17 eV and 3.75 eV. The variation of the molar TMAl flow from 3.5 to 35.4 µmol/min resulted in a AlN composition between 7.8% and 30.7% with an emission energy variation between 3.6 eV and 4.1 eV. Cathodoluminescence hyperspectral imaging provided evidence for the formation of nanoscale InN-rich regions. Analysing the emission properties of these InN-rich regions showed that their emission energy is inhomogeneous and varies by ≈150 meV. We provide evidence that the formation of these InN-rich regions is highly dependent on the AlN and InN composition of the layer and that their formation will strongly affect the performance of InxAlyGa1−x−yN LEDs.