Improvement of the emission properties from InGaN/GaN dot-in-a-wire nanostructures after treatment in the flowing afterglow of a microwave N₂ plasma

Nominally pure GaN nanowires (NWs) and InGaN/GaN dot-in-a-wire heterostructures were exposed to the flowing afterglow of a N₂ microwave plasma and characterized by photoluminescence (PL) spectroscopy. While the band-edge emission from GaN NWs and the GaN matrix of the InGaN/GaN NWs strongly decreased due to the creation of non-radiative recombination centers in the near-surface region, the emission from the InGaN dots strongly increased. PL excitation measurements indicate that such an increase cannot be explained by a plasma-induced shift of the GaN absorption edge. It is rather ascribed to the passivation of grown-in defects and dynamic annealing due to the presence of plasma-generated N atoms and N₂ metastables without excessive introduction of ion-induced damage. (paper)