We use photo-electron paramagnetic resonance (EPR) measurements and first-principles calculations to identify and explain the properties of carbon in AlN. We present clear evidence for carbon substitution on the nitrogen site (C$_{ \rm N}$). We also clarify the origin of a widely observed EPR spectra in AlN that, although often attributed to a deep donor defect, we demonstrate is surprisingly due to C$_{ \rm N}$. Finally, we show the presence of C$_{ \rm N}$ is consistent with the absorption spectra at 4.7 eV observed in AlN.
Categories: cond-mat.mtrl-sci