Band gaps of wurtzite ScxGa1-xN alloys

Optical transmittance measurements on epitaxial, phase-pure, wurtzite-structure Sc x Ga1− x N films with 0 ≤ x ≤ 0.26 showed that their direct optical band gaps increased from 3.33 eV to 3.89 eV with increasing x, in agreement with theory. These films contained I1- and I2-type stacking faults. However, the direct optical band gaps decreased from 3.37 eV to 3.26 eV for Sc x Ga1− x N films, which additionally contained nanoscale lamellar inclusions of the zinc-blende phase, as revealed by aberration-corrected scanning transmission electron microscopy. Therefore, we conclude that the apparent reduction in Sc x Ga1− x N band gaps with increasing x is an artefact resulting from the presence of nanoscale zinc-blende inclusions.