Analysis of the Dislocation and Polarity in an AlN Layer Grown Using Ga–Al Flux

We have developed a novel liquid-phase epitaxial (LPE) technique that uses Ga–Al flux to grow AlN layers on nitrided sapphire substrates. In this study, cross-sectional and plan-view images were taken using a transmission electron microscope. An edge dislocation was dominant in the LPE AlN layers; its density was approximately 5×109 cm-2. Convergent-beam electron diffraction analysis revealed that the LPE layer had Al polarity, even though the nitrided sapphire layer had N polarity. The oxygen potential in the injecting N2 gas played an important role in the polarity inversion in the LPE growth.