Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 45: GaN devices
HL 45.5: Vortrag
Donnerstag, 28. Februar 2008, 10:30–10:45, EW 202
GaInN/GaN quantum well laser structures emitting in the blue-green spectral range — •Daniel Dräger1, Uwe Rossow1, Holger Jönen1, David Schenk2, Jean-Yves Duboz2, and Andreas Hangleiter1 — 1Institute of Applied Physics, Technical University of Braunschweig, Germany — 2CRHEA-CNRS, Valbonne, France
Presently, GaN-based laser diodes are limited to the violet-blue region of the spectrum. Our aim is to obtain laser emission in the blue-green spectral range. In order to study GaInN-based laser structures, low pressure MOVPE was used to grow such structures on a variety of substrates (freestanding GaN, GaN templates, and SiC). This allows investigations of the influence of the substrate related dislocation densities on gain, losses and carrier recombination. Our samples were investigated by optical gain spectroscopy using the variable stripe length method.
In order to reach wavelengths longer than 450 nm an increase of the indium concentration to more than 25 % is needed. Such high In content requires careful optimization of the growth conditions in order to avoid damaging of the quantum wells by thermal stress. Combining the results of the gain measurement with a theoretical calculation of the gain spectra we determine the threshold power, carrier density and the carrier recombination times of the sample. On bulk GaN substrates we find threshold power levels as low as 20 kW/cm2. Up to now we obtain optical gain up to a peak wavelength of 465 nm with losses of about 30 cm−1. Our next targets are a wavelength of 480 nm as well as a further reduction of the threshold power.