Berlin 2024 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 52: Nitrides: Devices

HL 52.8: Vortrag

Freitag, 22. März 2024, 11:30–11:45, EW 015

Facet degradation mechanisms of InGaN-based laser diodes emitting around 420 nm — •Erik Freier, Jos Boschker, Johannes Glaab, Anna Mogilatenko, Carsten Netzel, Martin Guttmann, Ji Hye Kang, Saad Makhladi, and Sven Einfeldt — Ferdinand-Braun-Institut (FBH), Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany

There are numerous possible applications for InGaN-based laser diodes in the field of metrology and sensing. One example is an external cavity diode laser for a rubidium-based optical atomic clock for use in space. In order to realize such an experiment, a diode laser with an emission wavelength of 420 nm with high reliability and stability in terms of emitted output power and beam direction is a basic prerequisite. The facet coating has a significant influence on the laser properties. In long-term cw operation, we tested the reliability of ridge waveguide lasers with various facet coating material systems consisting of Al2O3, SiO2, TiO2, and Ta2O5, respectively, in different atmospheres. The facet degradation was investigated using scanning and transmission electron microscopy combined with energy dispersive x-ray spectroscopy. As a general effect, we observe the formation of a SiOx layer of several 100 nm thickness on the output facet during laser emission. This leads to fluctuations in the output power of the diode laser. We discuss several options to suppress this effect including the use of different coating material combinations, atmospheres and aging conditions. We present strategies to fabricate long-term stable facets of blue-violet lasers with a stable laser emission of 20 mW for thousands of hours.

Keywords: InGaN-based laser diodes; facet degradation; facet coating materials; reliability; scanning electron microscopy