Universal bandgap bowing in group-III nitride alloys

The energy gaps of molecular-beam-epitaxy grown wurtzite-structure In1−xAlxN alloys with x≤0.25 have been measured by absorption and photoluminescence experiments. The results are consistent with the recent discovery of a narrow bandgap of ∼0.7 eV for InN. A bowing parameter of 3 eV was determined from the composition dependence of these bandgaps. Combined with previously reported data of InGaN and GaAlN, these results show a universal relationship between the bandgap variations of group-III nitride alloys and their compositions.