Structural and optical properties of semipolar (1122) AlGaN grown on (1010) sapphire by metal-organic vapor phase epitaxy

J. Stellmacha, F. Mehnkea, M. Frentrupa, C. Reicha, J. Schlegela, M. Pristovseka, T. Wernickea, M. Kneissla,b

Published in:

J. Cryst. Growth, vol. 367, pp. 42-47 (2013).

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Abstract:

We report on the growth of semipolar (1122) AlGaN in the entire composition range on (1010) sapphire by metal-organic vapor phase epitaxy. Growth rates increase linearly with the metal-organic supply and have been realized up to 2.5 µm/h. The Al content determined by photoluminescence and transmission measurements depends linearly on the Al/Al+Ga ratio in the gas phase. The growth rate and the Al incorporation are higher for (1122) AlGaN than for (0001) AlGaN. This is attributed to different adatom mobility and desorption. The in-plane relationship of (1122) AlGaN is [1100]AlGaN|| [1210]Sap. and [1123]AlGaN|| [0001]Sap., as typical for semipolar nitrides on m-plane sapphire. For Al contents up to 60% triangle-like structures dominate the surface. For Al contents above 70% it transforms into an undulation along [1100] and additional dot-like structures. The smoothest surface morphologies with a rms roughnesses of 2 nm were achieved for Al mole fractions of ∼ 50%.

a Technische Universität Berlin, Institut für Festkörperphysik, Sekr. EW6-1, Hardenbergstr. 36, 10623 Berlin, Germany
b Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany

Keywords:

A3. Metalorganic vapor phase epitaxy; B1. Nitrides; B2. Semiconducting aluminium compounds; B2. AlGaN.