Abstract
Abstracta‐plane ($11{\bar {2}}0$) GaN thin films grown under various conditions on r‐plane sapphire by plasma‐assisted molecular beam epitaxy (PAMBE) were characterized by nanoindentation and transmission electron microscopy (TEM) techniques. It was found that the increase of the built‐in threading dislocation (TD) density induces an increase on the values of both the nanohardness (H) and the reduced elastic modulus (E*). Characteristic single ‘pop‐in’ discontinuities were detected on the loading segments of the load–unload cycle. The TDs appear to cause a decrease of the load for the onset of the pop‐in discontinuity. The dependence of the elastoplastic behaviour on the TD density is attributed to their sessile character, causing them to become obstacles for basal plane slip.
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