a-plane InN nanostructures were fabricated on a hole-patterned a-plane GaN template by electron-cyclotron-resonance plasma-excited molecular beam epitaxy (ECR-MBE). The growth temperature should be optimized to realize precise nucleation at the patterned holes with sufficient In desorption and a sufficiently long In migration length. Polarity determination clearly revealed that a-plane InN crystals have an anisotropic growth morphology. The InN growth rate in the N-polar [000–1] direction is higher than those in the In-polar  and [1–100] directions. a-plane InN nanowalls were fabricated by exploiting the different the growth rates in the 〈0001〉 and 〈1–100〉 directions.
SEM image of position-controlled a-plane InN nanostructures grown by ECR-MBE on a hole-patterned a-plane GaN template.