Growth optimization and doping with Si and Be of high quality GaN on Si(111) by molecular beam epitaxy |
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Authors: | M A Sánchez-García E Calleja F J Sanchez F Calle E Monroy D Basak E Muñoz C Villar A Sanz-Hervas M Aguilar J J Serrano J M Blanco |
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Affiliation: | (1) Dpto. Ingeniería Electrónica, ETSI Telecomunicación, UPM, Ciadad Universitaria s/n, 28040 Madrid, Spain;(2) Dpto. TSC e Ing. Telematica, ETSIT, Univ. Valladolid, Spain;(3) Dpto. Tecnología Electróniea, ETSI Telecomunicación, UPM, Ciudad Universitaria s/n, 28040 Madrid, Spain |
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Abstract: | GaN layers have been grown by plasma-assisted molecular beam epitaxy on AlN-buffered Si(111) substrates. An initial Al coverage
of the Si substrate of aproximately 3 nm lead to the best AlN layers in terms of x-ray diffraction data, with values of full-width
at half-maximum down to 10 arcmin. A (2×2) surface reconstruction of the AlN layer can be observed when growing under stoichiometry
conditions and for substrate temperatures up to 850°C. Atomic force microscopy reveals that an optimal roughness of 4.6 nm
is obtained for AlN layers grown at 850°C. Optimization in the subsequent growth of the GaN determined that a reduced growth
rate at the beginning of the growth favors the coalescence of the grains on the surface and improves the optical quality of
the film. Following this procedure, an optimum x-ray full-width at half-maximum value of 8.5 arcmin for the GaN layer was
obtained. Si-doped GaN layers were grown with doping concentrations up to 1.7×1019 cm−3 and mobilities approximately 100 cm2/V s. Secondary ion mass spectroscopy measurements of Be-doped GaN films indicate that Be is incorporated in the film covering
more than two orders of magnitude by increasing the Be-cell temperature. Optical activation energy of Be acceptors between
90 and 100 meV was derived from photoluminescence experiments. |
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Keywords: | III-nitrides molecular beam epitaxial (MBE) growth n-and p-type doping |
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