Abstract
Evidence for the presence of d-electron core relaxation effects in GaN and InN is examined by comparing the physical properties of these materials with those of AlN and the group III arsenides and phosphides. The comparison strongly suggests that d-electron core relaxation effects play an important role in the properties of the III–V nitride semiconductors. Based on these observations, it is proposed that Ca and C be investigated as dopants potentially superior to Mg for p-type doping of GaN.