Impact of High-Temperature Annealing on Boron Containing AlN Layers Grown by Metal Organic Vapor Phase Epitaxy
phys. stat. sol. (a), vol. 217, no. 16, pp. 2000251 (2020).
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Herein, the impact of high-temperature (HT) annealing on the crystalline structure of metal organic vapor phase epitaxy (MOVPE)-grown boron-containing AlN layers is investigated. High-resolution X-ray diffraction studies reveal AlBN in the wurtzite configuration for nonannealed 300 nm-thick layers containing several percent of boron. After 3 h of annealing at 1700°C, the AlBN-related reflex is weakened, showing a strong impact of the HT treatment on the crystalline structure of this material. After annealing, high-resolution transmission electron microscopy micrographs reveal grain formation with moiré patterns, giving strong evidence of different crystal phases or orientations, alongside well-oriented wurtzite regions. High-angle annular dark-field (HAADF) imaging and electron energy loss spectroscopy indicate stronger compositional inhomogeneities for the annealed sample in comparison with the as-grown layer, most likely related to phase separation between AlN and BN. In addition, a significant diffusion of B out of the surface region is observed. AlBN with about ten times a lower boron content, for which defect propagation from the AlN template into the AlBN layer is visible, shows a much more homogeneous contrast in HAADF investigations after annealing, although the formation of granular structures is still observed.
a Institute of Functional Nanosystems, Ulm University, Albert-Einstein-Allee 45, 89081 Ulm, Germany
b Central Facility of Electron Microscopy, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, German
c Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany
d Institute of Quantum Matter/Semiconductor Physics Group, Ulm University, Albert-Einstein-Allee 45, 89081 Ulm, Germany
AlBN, boron-III nitrides, high-temperature annealing, metal organic vapor phase epitaxy