High-quality AlN layer homoepitaxially grown on nitrided a-plane sapphire using a Ga-Al flux

We previously grew AlN layers with in-plane rotational domains on nitrided c-plane sapphire substrates using a Ga-Al flux method. In this study, we successfully grew rotational-domain-free AlN layers using nitrided a-plane sapphire substrates. The full width at half maximum values of the X-ray rocking curves of (0002) and (1012) of the AlN layer were 90 and 392 arcsec, respectively. From the results of transmission electron microscopy, edge-type dislocations were observed to be dominant in the layer. Convergent-beam electron diffraction revealed the occurrence of polarity inversion at the interface between the AlN layer and the nitrided sapphire.