Articles you may be interested in Investigation of the light-extraction efficiency in 280 nm AlGaN-based light-emitting diodes having a highly transparent p-AlGaN layer
We conducted a comprehensive investigation of dislocations in AlGaN. Using aberration-corrected scanning transmission electron microscopy and energy dispersive X-ray spectroscopy, the atomic structure and atom distribution at the dislocation core have been examined. We report that the core configuration of dislocations in AlGaN is consistent with that of other materials in the III-Nitride system. However, we observed that the dissociation of mixed-type dislocations is impeded by alloying GaN with AlN, which is confirmed by our experimental observation of Ga and Al atom segregation in the tensile and compressive parts of the dislocations, respectively. Investigation of the optical properties of the dislocations shows that the atom segregation at dislocations has no significant effect on the intensity recorded by cathodoluminescence in the vicinity of the dislocations. These results are in contrast with the case of dislocations in InGaN where segregation of In and Ga atoms also occurs but results in carrier localization limiting non-radiative recombination at the dislocation. This study therefore sheds light on why InGaN-based devices are generally more resilient to dislocations than their AlGaN-based counterparts.
The structural, chemical and electrical properties of Ni/Au contacts to atomic layer deposited α-Ga2O3 were investigated. Ni forms a Schottky contact with α-Ga2O3, irrespectively of the post-annealing temperature. No sign of metal oxidation was observed at the metal-semiconductor interface (unlike what is observed for other metals like Ti), and instead, the metallurgical processes of the Ni-Au bilayer dominate the electrical properties. It is found that 400-450oC is the optimal annealing temperature, which allows for metal diffusion to heal gaps at the metal/semiconductor interface, but is not sufficient for Ni and Au to significantly interdiffuse and form an alloy with compositional inhomogeneities.
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