Regensburg 2025 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 32: Nitrides: Preparation and Characterization I

HL 32.2: Vortrag

Mittwoch, 19. März 2025, 09:45–10:00, H15

Nanoscale characterization of cascaded GaN/InGaN LEDs with tunnel junction — •Konstantin Wein, Gordon Schmidt, Frank Bertram, Holger Eisele, Peter Veit, Olga August, Christoph Berger, Armin Dadgar, André Strittmatter, and Jürgen Christen — Otto-von-Guericke-University Magdeburg, Germany

In this work, comprehensive cathodoluminescence (CL) and electron beam induced current (EBIC) characterization directly performed in a scanning transmission electron microscopy (STEM) were performed on an InGaN/GaN double cascaded LED using a GaN:Ge/GaN:Mg tunnel junction (TJ). Cascaded LEDs benefit from monolithic multi-wavelength emission, lower injection current density (lower droop), and smaller chip sizes compared with standard LEDs. In low temperature (T = 17 K) highly spatially resolved CL, each individual layer is identified by its characteristic emission. The GaN:Si layers exhibit NBE emission at 365 nm corresponding to donor-bound exciton recombination, in contrast to the GaN:Mg layers which exhibit donor-acceptor pair recombination emitting at 380 nm. The intensity profile across the InGaN MQWs of both active regions gives access to the transport and capture of the excess carriers and excitons. The direct comparison of the local CL emission with the EBIC signal exhibits not only the local quantum efficiency as well as transfer of carriers (diffusion/drift) but also the current spreading/injection distribution of the vertical device. The impact of functional layers like electron blocking layers or TJs on the transport of carriers is directly visualized on the nano-scale.

Keywords: EBIC; GaN; cathodolumineszenz; STEM; LED