AlN with a wide bandgap of 6.2 eV is a promising candidate for ultraviolet light-emitting diodes and laser diodes. However, the production of the required p-type AlN is still challenging. As a possible dopant Cd was suggested among other Group II atoms (Be, Mg, and Zn). In this study the annealing condition of implanted Cd in AlN was investigated with the method of the perturbed angular correlation (PAC). Therefore radioactive 117Cd or 111mCd ions were implanted into thin AlN films on sapphire substrate with an energy of 30 keV and fluences in the range of 1011 ions/cm2.
After thorough annealing with a proximity cap of the same material most of the Cd-probes occupy substitutional lattice sites and almost all implantation damage can be annealed. This results in a distinct frequency in the PAC spectra which increases with temperature. In contrast to the formation of an indium nitrogen-vacancy complex observed with the probe 111In on substitutional Al-sites no defects are bound to substitutional Cd impurities. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)