Selective-area growth of GaN nanocolumns on titanium-mask-patterned silicon (111) substrates by RF-plasma-assisted molecular-beam epitaxy

The selective-area growth (SAG) of GaN nanocolumns by RF-plasma-assisted molecular-beam epitaxy is demonstrated by the use of Ti mask patterns on (111) Si substrates. At the growth temperature of 935 degrees C, the GaN nanocolumns grew only on the stripe windows where Si was exposed, and the growth of nanocolumns on the Ti surface was completely suppressed. The SAG of GaN occurred above approximately 900 degrees C, but below that no SAG occurred because GaN crystals nucleated on the Ti mask. When the window width was 120 nm, a single-nanocolumn was aligned along the Ti window.