Mechanism of GaN quantum dots capped with AlN:: An AFM, electron microscopy, and x-ray anomalous diffraction study

Capping of GaN quantum dots with AlN has been studied at the monolayer scale by combining atomic force microscopy, high resolution electron microscopy, and grazing incidence x-ray anomalous diffraction. Consistent with the results provided by these three techniques, it has been demonstrated that, following a wetting of the dots by an AlN layer up to 4 ML coverage, subsequent capping is dominated by a preferential AlN growth in between the dots, eventually resulting in a complete smoothing of AlN. Interdiffusion has been shown to be negligible during this process, which makes the GaN/AlN system unique among semiconductors.