Growth of $>$100 $\mu$m thick diamond layers adherent on aluminium nitride with low thermal boundary resistance between diamond and AlN is presented in this work. Thermal barrier resistance(TBR$_{\mbox{\tiny{eff}}}$) was found to be in the range of 16 m$^2$K/GW which is a large improvement on the current state-of-the-art. While thick films failed to adhere on untreated AlN films, hydrogen/nitrogen plasma treated AlN films retained the thick diamond layers. Clear differences in zeta potential measurement confirms surface modification due to hydrogen/nitrogen plasma treatment. An increase in non-diamond carbon in the initial layers of diamond grown on pre-treated AlN is seen by Raman spectroscopy. The presence of non- diamond carbon has minimal effect on the thermal barrier resistance. The surfaces studied with x-ray photoelectron spectroscopy (XPS) revealed a clear distinction between pre-treated and untreated samples. The surface aluminium goes from nitrogen rich environment to an oxygen rich environment after pre-treatment. A clean interface between diamond and AlN is seen by cross sectional transmission electron microscopy.

We present a multi-microscopy study of dislocations in InGaN, whereby the same threading dislocation was observed under several microscopes (atomic force microscopy, scanning electron microscopy, cathodoluminescence imaging and spectroscopy, transmission electron microscopy), and its morphological optical and structural properties directly correlated. We achieved this across an ensemble of defects large enough to be statistically significant. Our results provide evidence that carrier localization occurs in the direct vicinity of the dislocation through the enhanced formation of In-N chains and atomic condensates, thus limiting non-radiative recombination of carriers at the dislocation core. We highlight that the localization properties in the vicinity of threading dislocations arise as a consequence of the strain field of the individual dislocation and the additional strain field building between interacting neighboring dislocations. Our study therefore suggests that careful strain and dislocation distribution engineering may further improve the resilience of InGaN-based devices to threading dislocations. Besides providing a new understanding of dislocations in InGaN, this paper presents a proof-of-concept for a methodology which is relevant to many problems in materials science.