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HL: Fachverband Halbleiterphysik

HL 96: Poster III C (III-V Semiconductors incl. Nitrides)

HL 96.22: Poster

Donnerstag, 19. März 2015, 14:00–20:00, Poster B

Strain and surface morphology in AlGaN-based UV-C laser heterostructures — •F. Krueger¹, C. Kuhn¹, F. Mehnke¹, M. Martens¹, P. Schneider¹, V. Kueller², J. Park³, A. Knauer², J. Rass^1,2, T. Wernicke¹, M. Weyers², M. Lehmann³, and M. Kneissl^1,2 — ¹Technische Universität Berlin, Institut für Festkörperphysik, Germany — ²Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin, Germany — ³Technische Universität Berlin, Institut für Optik und Atomare Physik, Germany

UV laser diodes would be superior to conventional UV lasers in cost, size and robustness. However the realization of UV lasers has proven to be challeging due to insufficient n- and p-type doping as well as high dislocation densities in AlGaN/ sapphire heterostructures. In this work optically pumped AlGaN MQW lasers grown on defect reduced AlN/sapphire templates with lasing wavelengths between 250 nm and 280 nm are investigated. The surface morphology is strongly dependent on the growth conditions and exhibits step bunches, hillocks and V-pits. It was found, that the V-pit density correlates with the strain state of the QWs. By increasing the aluminum content in the QWs less strain is induced which leads to a reduced V-pit density and therefore less non-radiative recombination centers and mode losses. Additionally, the optimized QWs were embedded into a p-n-junction for current injection. For the p-side we investigated AlGaN:Mg cladding layers with an average aluminum content between 34%-81%. All heterostructures show electro-luminescence near 270 nm and increasing operation voltage with increasing aluminum content in the AlGaN cladding.