Regensburg 2019 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 24: Nitrides: Preparation and characterization I

HL 24.2: Vortrag

Mittwoch, 3. April 2019, 09:45–10:00, H31

Growth rate reduction of cubic III-nitrides at high doping levels in molecular beam epitaxy — •Michael Deppe¹, Jürgen W. Gerlach², Thomas Riedl¹, Jörg K. N. Lindner¹, Dirk Reuter¹, and Donat J. As¹ — ¹University of Paderborn, Department of Physics, Warburger Straße 100, 33098 Paderborn — ²Leibniz Institute of Surface Engineering (IOM), Permoserstraße 15, 04318 Leipzig

The most common donor for n-type doping of cubic GaN (c-GaN) is silicon. Recently we have also investigated germanium as an n-type donor for c-GaN and found that it is a well-suited alternative to silicon. We present the growth of c-GaN layers doped by Si and Ge up to the order of 10²⁰ cm⁻³. Layers are grown by plasma-assisted molecular beam epitaxy on 3C-SiC (001) substrates. Thicknesses of the c-GaN layers are determined by reflectometric interference spectroscopy and time-of-flight secondary ion mass spectrometry. We find that the growth rate remains constant up to donor concentrations around 10¹⁹ cm⁻³ and decreases at higher doping levels both with Ge and Si dopants. The growth rate of the highest Ge-doped sample is reduced by 40% compared to undoped samples and it is reduced by 23% for the highest Si doping. Additionally, Ge-doped c-Al_0.25Ga_0.75N layers are grown with donor concentrations comparable to the c-GaN layers. No reduction of the growth rate could be observed for c-Al_0.25Ga_0.75N. We suppose the growth rate reduction in c-GaN is among others due to higher bond dissociation energies of Ge-containing bonds compared to Ga-containing bonds. Dissociation energies of bonds involving Al however are higher, thus the effect is not observed in c-AlGaN.