Control of the epitaxial orientation and reduction of the interface leakage current in YMnO₃/GaN heterostructures

Epitaxial ferroelectric YMnO3 (YMO) thin films with high crystalline quality were fabricated on (0001) GaN substrates by pulsed laser deposition followed by rapid thermal annealing. X-ray diffraction and transmission electron microscopy measurements reveal that YMO layers are of (0001) orientation with an in-plane epitaxial relation (0001)(YMO) parallel to (0001)(GaN), [11 (2) over tilde0](YMO) parallel to [11 (2) over tilde0](GaN). The orientation of the lattice of YMO was found to be controlled by the annealing conditions. Y2O3 nanocrystallites observed near the interface were possible seeds to stabilize the orientation of the epitaxial YMO thin films. The appropriate annealing treatment could improve the crystalline quality and reduce the interface leakage current.