In situ measurements of the critical thickness for strain relaxation in β-GaN/MgO structures

It is demonstrated by in situ reflection high-energy electron diffraction (RHEED) studies that the growth of cubic GaN on MgO occurs in a layer-by-layer mode under Ga-rich conditions, growth rates 0.25-0.30 ML/s and 700 °C substrate temperature. From streak-spacing analysis of the observed RHEED patterns, it is possible to infer that the GaN layer grows pseudomorphically on MgO up to 3 monolayers (ML). After that, a relaxation process begins and the layer-by-layer or 2-dimensional growth changes to a columnar or 3-dimensional growth, as evidenced by the transformation of the RHEED patterns, which change from streaky to spotty. The experimental critical thickness (hc) value of 3 ML is close to the prediction of the Frank-van der Merwe classical model of 2.5 ML. Other models predict hc values 3-6 times the experimental value experimentally observed. © 2008 Elsevier B.V. All rights reserved.

A3. Molecular beam epitaxy; B1. Nitrides; B2. Semiconducting III-V materials Crystal growth; Gallium nitride; Molecular beam epitaxy; Molecular beams; Molecular dynamics; Reflection high energy electron diffraction; Semiconducting gallium; Semiconductor growth; Semiconductor quantum wires; 3-dimensional; A3. Molecular beam epitaxy; B1. Nitrides; B2. Semiconducting III-V materials; Classical models; Critical thickness; Experimental values; Ga-rich conditions; Gan layers; In-situ; In-situ measurements; Layer by layers; Layer-by-layer modes; Substrate temperatures; Gallium alloys

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