Self-Assembly Semipolar AlN Nanopyramids Grown on Powder-Compressed AlN Substrates

AlN nanopyramids with semipolar facets are grown by metal-organic chemical vapor deposition (MOCVD) on the AlN substrate attained with compressed AlN powders. Surface qualities of the polycrystalline substrate are improved with an AlN buffer layer deposited by sputtering, followed by appropriate post annealing. It is found that a pulsed flow condition of ammonia (NH₃) during the MOCVD growth can effectively enhance morphologic uniformity and crystallinity of the nanopyramids. The semipolar AlN nanopyramids serve as a promising template for ultraviolet emitters, considering their increased surface area and reduced polarization fields.