Progress in the preparation of aluminum nitride substrates from bulk crystals

Large (11-mm diameter) single-crystal AlN boules have been prepared using sublimation-recondensation growth. X-ray topography shows that substrates prepared from those boules have a dislocation density of less than 500 cm^-2, while the central region of these substrates was nearly dislocation-free. Rocking curves of less than 10 arcsecs have been obtained indicating the high quality of these crystals. The AlN substrates have been used to growth an AlGaN/AlN multi-quantum well structure with excellent crystalline quality and with photoluminescence peaked at around 260 nm. In addition, a UV LED with emission wavelength at 360 nm has been fabricated. This is the first operating opto-electronic device demonstrated on an AlN substrate.