We have grown AlN crystals by a sublimation process. As grown AlN boules were grown as polycrystals because a seed crystal was not used. The size of the crystallites was 0.2-1 mm and the color was dark green. The as-grown AlN boule had a length of about 2-3 mm. Carbon impurities were observed on its surface while they could not be inside the as-grown AlN boule. The growth behavior and the morphology of the crystallites were investigated by an optical microscope, SEM observations and Xray diffraction(XRD). Photoluminescence (PL) measurements were carried out in order to characterize the optical properties. We could obtain a 204 nm deep UV emission peak from an excitation wavelength of 202 nm.

Keywords: AlN, LEDs, crystal growth, sublimation process, photoluminescence (PL).