Dresden 2009 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 41: GaN: preparation and characterization II

HL 41.11: Talk

Thursday, March 26, 2009, 12:30–12:45, BEY 154

Growth modes of thick InGaN films on GaN — •Martin Leyer, André Kruse, Joachim Stellmach, Markus Pristovsek, and Michael Kneissl — Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, 10623 Berlin

We have investigated the growth of thick (d > 10 nm) InGaN layers grown by metal-organic vapour phase epitaxy (MOVPE). The composition was controlled by varying the growth temperature between 700 ^∘C and 850 ^∘C. The indium content and the strain was determined by X-ray diffraction. We observed two distinct peaks in the ω-2Θ scans for most of the samples. For lower growth temperatures a relaxed top layer was found in reciprocal space maps. For higher growth tempratures a lateral decomposed top layer was observed. The variation of the indium content with growth temperature was exponential.

We propose the following model: In a first step a smooth strained InGaN wetting layer is grown in the Stranski-Krastanov growth mode. Then a transition from 2D to 3D growth takes place. For growth temperatures below 750 ^∘C a rough layer is grown pseudomorphic up to the crititcal layer thickness and subsequently relaxes. For growth temperatures above 750 ^∘C a strained, but laterally inhomogeneous layer is grown.

For the strained layer the activation energy for indium incorporation was ∼2.2 eV and for the relaxed layer ∼0.6 eV. Growth rate(s) and the critical thickness(es) were obtained by in-situ ellipsometry.