title: Homogeneity and composition of AlInGaN: A multiprobe nanostructure study.
abstract: The electronic properties of quaternary AlInGaN devices significantly depend on the homogeneity of the alloy. The identification of compositional fluctuations or verification of random-alloy distribution is hence of grave importance. Here, a comprehensive multiprobe study of composition and compositional homogeneity is presented, investigating AlInGaN layers with indium concentrations ranging from 0 to 17at% and aluminium concentrations between 0 and 39 at% employing high-angle annular dark field scanning electron microscopy (HAADF STEM), energy dispersive X-ray spectroscopy (EDX) and atom probe tomography (APT). EDX mappings reveal distributions of local concentrations which are in good agreement with random alloy atomic distributions. This was hence investigated with HAADF STEM by comparison with theoretical random alloy expectations using statistical tests. To validate the performance of these tests, HAADF STEM image simulations were carried out for the case of a random-alloy distribution of atoms and for the case of In-rich clusters with nanometer dimensions. The investigated samples, which were grown by metal-organic vapor phase epitaxy (MOVPE), were thereby found to be homogeneous on this nanometer scale. Analysis of reconstructions obtained from APT measurements yielded matching results. Though HAADF STEM only allows for the reduction of possible combinations of indium and aluminium concentrations to the proximity of isolines in the two-dimensional composition space. The observed ranges of composition are in good agreement with the EDX and APT results within the respective precisions.
authors.affiliation: Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany. Electronic address: f.krause@ifp.uni-bremen.de.
authors.forename: Florian F
authors.initials: FF
authors.lastname: Krause
authors.affiliation: OSRAM Opto Semiconductors GmbH, Leibnizstr. 4, 93055 Regensburg, Germany.
authors.forename: Jan-Philipp
authors.initials: JP
authors.lastname: Ahl
authors.affiliation: Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Str. 1, 40237 Düsseldorf , Germany.
authors.forename: Darius
authors.initials: D
authors.lastname: Tytko
authors.affiliation: Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Str. 1, 40237 Düsseldorf , Germany.
authors.forename: Pyuck-Pa
authors.initials: PP
authors.lastname: Choi
authors.affiliation: EMAT, Universiteit Antwerpen, Groenenborgerlaan 171, 2020 Antwerpen, Belgium.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Egoavil
authors.affiliation: Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Schowalter
authors.affiliation: Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Mehrtens
authors.affiliation: Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany.
authors.forename: Knut
authors.initials: K
authors.lastname: Müller-Caspary
authors.affiliation: EMAT, Universiteit Antwerpen, Groenenborgerlaan 171, 2020 Antwerpen, Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Verbeeck
authors.affiliation: Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Str. 1, 40237 Düsseldorf , Germany.
authors.forename: Dierk
authors.initials: D
authors.lastname: Raabe
authors.affiliation: OSRAM Opto Semiconductors GmbH, Leibnizstr. 4, 93055 Regensburg, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Hertkorn
authors.affiliation: OSRAM Opto Semiconductors GmbH, Leibnizstr. 4, 93055 Regensburg, Germany.
authors.forename: Karl
authors.initials: K
authors.lastname: Engl
authors.affiliation: Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Rosenauer
keywords: APT; AlGaInN; AlInGaN; EDX; HAADF STEM; Homogeneity; InAlGaN