Berlin 2008 – wissenschaftliches Programm
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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.