Regensburg 2025 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 32: Nitrides: Preparation and Characterization I

HL 32.5: Talk

Wednesday, March 19, 2025, 10:30–10:45, H15

Nanoscale multi-spectroscopic characterisation of InGaN pseudo-substrates grown on nanowire arrays — •Aidan Flynn Campbell, Jingxuan Kang, Huaide Zhang, Oliver Brandt, Lutz Geelhaar, and Jonas Lähnemann — Paul-Drude-Institut für Festkörperelektronik, Berlin, Deutschland

The efficiency of nitride light-emitting diodes (LEDs) in the amber and red spectral ranges is severely limited by the high strain in (In,Ga)N quantum wells with increasing In content when grown on GaN. Thus, reducing the lattice mismatch between the active region and adjacent layers is highly desirable. Our approach exploits the lateral elastic strain relaxation facilitated by nanowires fabricated top-down from a single-crystalline layer, epitaxial overgrowth of a subsequent layer achieves a strain free pseudo-substrate. In this study, we characterise the optical, chemical, and crystallographic properties of such overgrown layers, which are key in understanding and optimising our epitaxial overgrowth fabrication route.

We utilise experimental techniques such as continuous-wave and time-resolved cathodoluminescence (TRCL), energy-dispersive X-ray spectroscopy (EDX), and high-resolution electron backscatter diffraction (HR-EBSD). We demonstrate low dislocation densities, low compositional variations and low crystal misorientation across coalescence boundaries. Furthermore, the factors influencing defect formation and the relevance of dislocation propagation are investigated and correlated with the resulting luminescence efficiency of the overgrown layers.

Keywords: pseudo-substrates; time-resolved cathodoluminescence; nanowires; InGaN; electron microscopy