Growth of AIN crystals by a sublimation process and their optical properties

We have grown AIN crystals by a sublimation process. As grown AIN 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 AIN 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 AIN boule. The growth behavior and the morphology of the crystallites were investigated by an optical microscope, SEM observations and X-ray 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.