InN epitaxial growths on Yttria stabilized zirconia (111) step substrates

We have performed epitaxial growths of InN on Yttria stabilized zirconia (YSZ) (111) substrates which have steps and atomically flat terraces using pulsed laser deposition (PLD). The epitaxial relationship between InN and YSZ turns out to be InN [1100]//YSZ [110] and InN [0001]//YSZ [111], which gives a small lattice mismatch of 2.3%. We have found that the full width at half maximum (FWHM) for the InN 2024 x-ray rocking curve is 980 arcseconds. Transmission electron microscopy (TEM) observations have revealed that the threading dislocation density in the InN films is less than 1×10⁹ cm^-2 and the InN/YSZ hetero-interface is atomically abrupt. We have also found that the lattice relaxation starts from the beginning of the growth and ends at a film thickness of approximately 5 nm. After the lattice relaxation, the surface flatness is restored and the growth proceeds in the layer-by-layer mode.