AlN epilayers and nanostructures growth in a homebuilt alumina hot-wall high temperature chemical vapor deposition system

AlN epilayers and nanostructures were grown in the range from 500 to 1500 °C in a homebuilt alumina hot-wall high temperature chemical vapor deposition system. The results revealed that high quality AlN epilayers can be grown at high temperature beyond 1100 °C and versatile AlN nanostrctures can be grown at low temperature below 900 °C, enabling the system to tailor AlN structures just by changing the growth temperature. High growth temperature as well as low N/Al ratio was preferable to surface mobility of the adatoms and lateral growth, resulting in a series of morphology changes. Meanwhile, the crystal quality improved with the increasing growth temperature, as proved by the decreasing FWHM of (0002) plane rocking curve of the epilayer and narrowing peaks in θ-2θ XRD pattern of the nanostructures. The epitaixal relationship was proven to be AlN (0001) ‖ sapphire (0001) and AlN [1-210] ‖ sapphire [1-100]. The layer was in tensile stress state in several tens of nanometers range near the interface and turned into compressive stress state out of the range. Tens of atoms layers of sapphire interface were substituted for AlN lattice due to nitridation. Low growth temperature produced versatile AlN nanostructures, whose crystal structures varied from amorphous in 500 °C case to defective crystal in 700 °C case and improved crystallinity in 900 °C case.