Regensburg 2022 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 30: Poster 2

HL 30.13: Poster

Donnerstag, 8. September 2022, 11:00–13:00, P3

Aging of GaN-based laser diodes investigated by micro-EL and micro-PL spectroscopy — •Lukas Uhlig¹, Conny Becht¹, Erik Freier², Ji-Hye Kang², Veit Hoffmann², Christoph Stölmacker², Sven Einfeldt², and Ulrich T. Schwarz¹ — ¹Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany — ²Ferdinand-Braun-Institut gGmbH, Leibniz-Institut für Höchstfrequenztechnik, 12489 Berlin, Germany

For the work towards long-time reliable GaN-based ridge waveguide laser diodes it is essential to understand the specific degradation effects that occur after some time of operation. Among the reported aging mechanisms are the generation of point defects in the active layer and a decrease in p-side conductivity.

To clarify this, we compare a previously stressed device with a similar but unstressed laser diode using micro-electroluminescence (EL) and confocal micro-photoluminescence (PL) spectroscopy. The devices are mounted p-side-down and the metal layer on the n-side is polished away to allow optical characterization in the plane of the quantum wells.

In contrast to the homogeneous EL-emission from the non-stressed device, the stressed laser diode exhibits bright and dark areas along the ridge on the scale of few 10 µm. The systematic correlation of high intensity with a spectral blue-shift and vice versa indicates local changes in the charge carrier density that we attribute to inhomogeneous electrical pumping. The micro-PL-measurements show an increased defect density in the active region.