Uniform N-Polar III-Nitrides on Si(111) by MBE

The importance of growth conditions for N-polar nitride MBE growth on Si is examined. It is found that metal-rich conditions at the initiation of growth lead to Al-Si eutectic formation. The eutectic can cause holes in the substrate and AlN layer, and floats on the nitride surface but can be incorporated into the nitride if the growth becomes N-rich. The inclusion of Si from the eutectic can cause polarity inversion, with greater levels of Si and inversion found in samples initiated with higher Al levels and, therefore, higher levels of eutectic formation. Evidence of eutectic was not found in samples where growth was started close to stoichiometry. In addition, the eutectic related defects in the nitride buffers typically did not propagate into nanostructures grown on them by selective area growth.