Effect of light irradiation on indentation‐induced dislocation behavior in GaN oriented for basal slip

Abstract The impact of external light on dislocation‐based plasticity in inorganic compound semiconductors has been increasingly recognized. Here, we investigated the effect of light on the dislocation behavior in wurtzite GaN oriented for basal slip using photoindentation. Two types of nanoindentation tests were performed in darkness and in 380 nm light on GaN single‐crystal substrates oriented to maximize the Schmid factor for the basal slip. Distinct pop‐in events were observed in the loading segment at loads of 150‒340 . Analysis of the first pop‐in events revealed that they correspond to homogeneous dislocation nucleation and are largely unaffected by light irradiation. Indentation creep tests at 2 mN showed that both creep depth and creep strain rate decreased in 380 nm light. Cross‐sectional ultra‐high voltage electron microscopy images taken beneath the indentation imprints displayed an asymmetric dislocation distribution with the majority aligned along the direction. A significant reduction in the density of indentation‐induced dislocations in 380 nm light was observed, indicating that light irradiation effectively suppresses dislocation glide motion and multiplication in GaN for basal slip.