Highly conductive n-AlxGa1-xN layers with aluminum mole fractions above 80%

F. Mehnke1, T. Wernicke1, H. Pingel1, C. Kuhn1, C. Reich1, V. Kueller2, A. Knauer2, M. Lapeyrade2, M. Weyers2, and M. Kneissl1,2

Published in:

Appl. Phys. Lett., vol. 103, no. 212109 (2013).

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Abstract:

Silicon doping of AlxGa1-xN layers with high aluminum mole fractions (0.8<x<1) was studied. The AlGaN:Si layers were pseudomorphically grown by metalorganic vapor phase epitaxy on low defect density epitaxially laterally overgrown AlN/sapphire templates. The effects of SiH<sub>4/III ratio and aluminum content on the resistivity, the carrier concentration, and the mobility have been investigated. By variation of the SiH4/III ratio during the growth of AlxGa1-xN:Si layers, a recorded low resistivity of Al0.81Ga0.19N:Si was obtained with 0.026Ωcm. The resistivity increases exponentially with increasing aluminum content to 3.35 Ω cm for Al0.96Ga0.04N, and the optimum SiH4/III ratio is shifted towards lower values. Hall effect measurements show that the increase of the resistivity with increasing aluminum mole fraction is mainly caused by a decrease of the carrier density. The optimized Al0.81Ga0.19N:Si exhibits a carrier concentration of 1.5×1019 cm-3 and a mobility of the carriers of 16.5 cm2V-1 s-1.

1 Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, EW 6-1, 10623 Berlin, Germany
2 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany