Regensburg 2016 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 99: Gallium Nitride: Devices

HL 99.8: Vortrag

Freitag, 11. März 2016, 12:00–12:15, H17

Smooth and uniform Al_0.8Ga_0.2N:Si superlattice cladding layers for UV-C laser diodes — •C. Kuhn¹, T. Simoneit¹, M. Martens¹, F. Mehnke¹, J. Enslin¹, K. Bellmann¹, A. Knauer², T. Wernicke¹, M. Weyers², and M. Kneissl^1,2 — ¹Technische Universität Berlin, Institut für Festkörperphysik, Berlin, Germany — ²Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin, Germany

For deep UV laser diodes the current injection, light absorption and waveguiding are key challenges. For efficient waveguiding smooth and abrupt interfaces are required, to avoid losses associated with light scattering. This paper investigates the influence of the growth process on the morphology and the conductivity of Al_0.8Ga_0.2N:Si n-cladding layers. We recently demonstrated highly conductive n-AlGaN single layers with sheet resistance of 0.026 Ωcm. However, these AlGaN layers exhibited relatively rough morphologies with large spirals of 30 nm height caused by the high growth rates. Additionally Al_xGa_1−xN:Si layers with x≤0.8 exhibit noticeable compositional fluctuations. In this paper we explore the use of AlGaN super lattices (SL), as well as growth interruptions (GRI) between the SL layers in order to reduce the roughness of the surface. XRD measurements exhibit well-ordered growth of the 2 nm/2 nm thick SL layers with average composition of x=0.8 and distinct satellite peaks in the XRD spectrum, without any indication for compositional fluctuations. The RMS roughness on 10x10 µ m² decreases from 7.0 nm without SL, to 3.7 nm with SL and 2.5 nm with 10 s GRI and obtaining the high conductivity constant.