Berlin 2024 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 13: Poster I
HL 13.7: Poster
Montag, 18. März 2024, 15:00–18:00, Poster E
Cathodoluminescence study of point and structural defects in bottom-up GaN nanowires — •Mikel Gómez Ruiz1, Matt Brubaker2, Kris Bertness2, Manfred Ramsteiner1, Oliver Brandt1, and Jonas Lähnemann1 — 1Paul-Drude-Institut für Festkörperelektronik, Germany — 2National Institute of Standards and Technology, USA
Luminescence techniques are inherently sensitive to the presence of both radiative and nonradiative defects. In this work, we investigate the prevalence and distribution of both point and structural defects in GaN nanowires (NWs) by low-temperature (10 K) cathodoluminescence (CL) hyperspectral line scans along the NW axis. Ordered arrays of NWs are grown by selective-area molecular beam epitaxy using a Si3N4 mask on a N-polar GaN template on Si. The CL intensity of single NWs is observed to vary along the NW axis. During initial NW growth, impinging Ga atoms can react with the Si3N4 mask leading to the unintentional incorporation of Si into the NW. The incorporation is gradually reduced once the NW height is approximately equal to their distance, where shadowing prevents the direct impingement of Ga atoms on the mask. The Fermi-level pinning at the NW side facets results in internal electric fields, whose spatial extent depends on the Si concentration and the NW diameter. These fields can dissociate excitons as well as shallow donors and acceptors, thus reducing the corresponding radiative emission intensity. A gradient in Si doping can thus explain the change in emission intensity. This Si doping also causes most of the NWs to have inversion domain boundaries.
Keywords: Point & structural defects; Bottom-up nanowires; Cathodoluminescence