Nanoheteroepitaxy of GaN on columnar SiC substrates by metalorganic chemical vapor deposition

Preliminary results on nanoheteroepitaxy of GaN on silicon face (Si-face) and carbon face (C-face) nanocolumnar SiC (CSC) by metalorganic chemical vapor deposition (MOCVD) are reported. The CSC substrates are fabricated from standard SiC wafers by photo-enhanced electrochemical etching, with typical diameter of pores around 20nm. Noticeable reduction of threading dislocations (IDs) in GaN is realized on the CSC substrates. On the C-face CSC, GaN nuclei have an inverted pyramidal shape which contains high density of stacking faults (SFs). These SFs block possible extension of IDs into upper portion of the layer. On the Si-face CSC, TDs are annihilated by forming nanoscale TD half-loops over the surface pores. These nanoscale TD loops confine the defective layer in GaN to within ∼50 nm thickness from the GaN/CSC interface. High density (∼5×10⁸ cm^-2) of remnant TDs still presents in GaN grown on CSC, chiefly because the surface damages on CSC were not properly removed before growth.