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HL: Fachverband Halbleiterphysik

HL 35: Poster I

HL 35.37: Poster

Dienstag, 8. März 2016, 15:00–19:00, Poster A

Influence of the p-AlGaN superlattice on the performance characteristics of deep UV laser diode heterostructures — •E. Ziffer¹, M. Martens¹, C. Kuhn¹, T. Simoneit¹, J. Rass¹, T. Wernicke¹, A. Knauer², V. Kueller², M. Weyers², S. Einfeldt², and M. Kneissl^1,2 — ¹Technische Universität Berlin, Institut für Festköperphysik, Berlin, Germany — ²Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin, Germany

AlGaN-based deep UV laser diodes (LD) require p-AlGaN cladding layers (CL) with high Al mole fractions. However, with increasing Al content the ionization energy of Mg dopants in AlGaN layers also increases, leading to high series resistance. We have investigated the influence of the p-side CL on AlGaN-based LD structures. The heterostructures consist of AlGaN multiple quantum well (MQW) active regions emitting near 270 nm, embedded in Al_0.70Ga_0.30N waveguide layers, an Al_0.80Ga_0.20N:Si n-CL and different AlGaN:Mg p-CLs, including a 200 nm thick AlGaN layer, 150 - 200 nm superlattices (SL) with different Al contents and a p-GaN contact layer. The structures were analyzed by transfer length method, I-V characterization and electroluminescence spectroscopy. All diodes exhibit dominant QW emission with peak wavelengths between 258  nm and 276  nm. By increasing the average Al content of the p-SL from 37% to 81%, the diodes’ turn-on voltage increases from 17 V to 26 V, whereas the series resistance stays constant on average (60 Ω for a contact size of 100x100 µ m²). This is an improvement in series resistance by one order of magnitude compared to LDs with a bulk Al_0.81Ga_0.19N p-CL.