Room-temperature epitaxial growth of AlN films

Abstract

We have grown AlN films on nearly-lattice-matched (Mn,Zn)Fe2O4 (111) substrates by pulsed-laser deposition at room temperature and investigated their structural properties using reflection high-energy electron diffraction (RHEED), grazing incidence angle x-ray reflectivity (GIXR), grazing incidence angle x-ray diffraction (GIXD), and atomic force microscope. We have found that AlN grows epitaxially even at room temperature. In situ RHEED observations have shown that the room-temperature growth of AlN starts with the two-dimensional mode followed by a transition to the three-dimensional mode at the film thickness of 2 nm. GIXR and GIXD measurements have revealed that the heterointerface between AlN and (Mn,Zn)Fe2O4 is abrupt and approximately 90% of the lattice mismatch is released at the interface due to the introduction of crystalline defects such as misfit dislocations. These results indicate that the present technique solves one of the two major problems with heteroepitaxial growths of group III nitrides (mismatch in the thermal expansion coefficients) and alleviates the other problem (mismatch in the lattice constants).