AlxGa1-xN nanowires (NWs) are considered to be a promising solution for solid-state ultraviolet (UV) emission. The basic physics of ternary alloys in NWs, and in particular of AlGaN NWs is however still to be explored.
Here we report on the study of the structural and optical properties of AlGaN sections grown on top of GaN NWs on Si (111) substrates by plasma-assisted molecular beam epitaxy, in particular as a function of AlGaN growth temperature and ternary alloy composition
Several series of samples with AlxGa1-xN sections on top of GaN NWs were grown in N-rich conditions, at different average AlN molar fractions (x in the 0.3-0.6 range) and various growth temperatures.
Microphotoluminescence of single nanowires reveals a broad spectrum made of sharp lines with linewidths in the 1-5 meV range. This is similar to what one obtains when probing in luminescence an ensemble of quantum dots. We thereafter performed photon correlation measurements in a Hanbury-Brown and Twiss set-up, which showed that indeed, antibunching is observed when probing a single line. Such a single AlGaN nanowire thus behaves as a collection of quantum dots, which we attribute to localization centers due to Ga-richer regions in the AlGaN matrix.
The mere counting of the number of sharp lines observed thus allows to determine the spatial density of such localized emission centers. We will also discuss time-resolved photoluminescence on such sharp emission lines, which allows to directly probe the size homogeneity of these localization centers in the AlGaN alloy.
Matthias Belloeil, Bruno Daudin, and Bruno Gayral, "Quantum-dot like localization in AlGaN nanowires (Conference Presentation)," Proc. SPIE 10104, Gallium Nitride Materials and Devices XII, 101040W (Presented at SPIE OPTO: January 31, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2250329.5391659241001.
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