Dresden 2014 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 89: Metamorphic structures: Bringing together incompatible materials I (Focus session with DF)

HL 89.4: Vortrag

Donnerstag, 3. April 2014, 10:45–11:00, POT 251

Strain engineering in a-plane GaN - Investigations on anisotropic strain behaviors — •Matthias Wieneke, Martin Feneberg, Michael Winkler, Peter Veit, Armin Dadgar, Jürgen Bläsing, Rüdiger Goldhahn, and Alois Krost — Otto-von-Guericke-Universität Magdeburg, FNW/IEP, Universitätsplatz 2, 39106 Magdeburg

The use of low temperature AlN interlayers (LT AlN) is a successful technique to prevent crack formation in thick c-plane GaN films, but also to reduce the density of basal plane stacking faults in semi-polar GaN. Here, we studied the impact of LT AlN on a-plane GaN films grown by metal-organic vapor-phase epitaxy on 2-inch r-plane sapphire substrates. The curvature increases during the growth of tensely-strained a-plane GaN buffer layers, while it decreases after inserting LT AlN. However, an increasing asphericity evaluated by a 3-spot-curvature measurement indicates an anisotropic strain relaxation. Consequently, after cooling-down various ex-situ X-ray diffraction (XRD) measurements reveal an increase in compressive strain along the in-plane GaN m-direction, while it marginally decreases along the in-plane GaN c-direction for layers with a LT AlN interlayer. The non-biaxial strain behavior mirrors in energy shifts of the characteristic photoluminescence features which is compared to the results of 4-band k· p theory. Furthermore, XRD and transmission electron microscopy measurements exhibit a degradation in the crystalline quality of GaN layers grown on LT AlN interlayer.