Epitaxial growth of indium nitride on (0001) sapphire

There is a large lattice mismatch between InN and sapphire. As a result, epitaxial growth of InN on sapphire is difficult and a two-step growth process was used. In the present study low-temperature InN nucleation layers (NLs) were grown on (0001) sapphire using metalorganic chemical vapor deposition (MOCVD) between 400-500 degrees Celsius with a V/III ratio of 30000. Samples were evaluated using scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). AFM and TEM images reveal that the NL deposited at 475 degrees Celsius had the highest density of nucleation islands. The NL is not continuous and consists of separated islands. Some islands are misoriented from the sapphire as indicated by the selected area diffraction pattern (SADP). After annealing at 600 degrees Celsius, the nucleation island density increases due to evaporation and re-deposition of InN. The annealed NL also is not continuous and still contains misoriented islands.;Epitaxial InN layers were grown at temperatures between 550-650 degrees Celsius with a V/III ratio of 15000. It was found that the AFM root mean square (RMS) roughness increased with increasing growth temperature as vertical InN growth was favored over lateral growth at higher temperatures. InN (0002) x-ray rocking curves showed the best full width at half maximum (FWHM) of 957 arcsec at the InN epitaxial growth temperature of 600 degrees Celsius. To enhance the lateral growth of InN at 600 degrees Celsius, the V/III ratio was reduced from 15000 to 10000. This improved the AFM RMS roughness from 52 nm at 15000 to 21 nm at 10000, but the FWHM (0002) rocking curve did not improve. Results from photoluminescence (PL) show emission at 0.8 eV.;Early stages of InN epitaxial growth show that growth occurs in patches of well aligned islands while misoriented islands do not grow. No dislocations are observed at boundaries of coalesced islands indicating that dislocations are not formed by InN island coalescence. TEM reveals that threading dislocations are present in the NL before and after annealing. These threading dislocations continue into the epitaxial growth.