Berlin 2024 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 44: Nitrides: Preparation and characterization II
HL 44.6: Vortrag
Donnerstag, 21. März 2024, 15:15–15:30, EW 015
Alloying and demixing in AlGaN/GaN nanowire heterostructures — •Rudolfo Hötzel1, Lukas Lübken1, Anton Schäning1, Florian Krause1, Andreas Rosenauer1,2, Stephan Figge1, and Martin Eickhoff1,2 — 1Institute of Solid State Physics, University of Bremen, 28359 Bremen, Germany — 2MAPEX, University of Bremen, 28359 Bremen, Germany
Contrary to common knowledge that GaN nanowires (NW) only grow in the nitrogen-rich (N-rich) regime, a precise evaluation of the growth stoichiometry on the growth surface shows a growth window extending into the metal-rich regime. The AlGaN/GaN NW heterostructures grown by molecular beam epitaxy were analyzed by scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX) as well as X-Ray diffraction (XRD). In that line, the influence of the III/V-ratio on the alloy formation of the ternary material for N-rich as well as metal-rich growth conditions is studied. In N-rich growth conditions the concentration in the alloy follows a linear trend up to close to the stoichiometric point of GaN, where the increased presence of Al leads to a change of surface adsorption which tips the growth over to the metal-rich regime, where we observe instantaneous growth of pure AlN despite the available Ga flux. However, after some time the growth switches over to incorporate Ga, forming an AlGaN alloy. In other words, even though Al possesses a higher reaction enthalpy and AlN forms, Ga accumulates on the growth surface resulting in another tip-over of the growth regime leading to AlGaN formation.
Keywords: Nanowires; AlGaN/GaN; Alloying; Demixing; MBE growth