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HL: Fachverband Halbleiterphysik

HL 45: GaN devices

HL 45.4: Vortrag

Donnerstag, 28. Februar 2008, 10:15–10:30, EW 202

Spectral Identification of Filaments in Broad Ridge 405 nm (Al,In)GaN Laser Diodes — •Harald Braun¹, Hans-Michael Solowan¹, Dominik Scholz¹, Tobias Meyer¹, Ulrich Theodor Schwarz¹, Stefanie Brüninghoff², Alfred Lell², and Uwe Strauß² — ¹NWF II - Physik, Universität Regensburg — ²Osram Opto Semiconductors GmbH, Regensburg

In broad area (Al,In)GaN laser diodes (LDs) with ridge widths larger than a few micrometer the laser mode in the waveguide builds up fi-laments, which influence the far field of the LD. Employing temporal and spectral resolved scanning near-field optical microscopy (SNOM) on pulsed electrically driven LDs we analyse the lateral mode profile on a nanosecond to microsecond timescale. Furthermore we are able to resolve the single Fabry-Perot modes of the laser mode correlated to the lateral position in the ridge waveguide. Different filaments have slightly different effective refractive indices and thus show up as separate longitudinal mode combs. In this way we can reconstruct the optical mode in the waveguide as a superposition of filaments, identified by their spectral fingerprint. Different samples, grown on SiC and GaN substrates, respectively, were investigated. The measurements show similar results for all samples concerning the lateral mode profile, whereas the samples grown on GaN substrate exhibit a less chaotic behaviour in the temporal and spectral regime compared to the LDs grown on SiC substrate.