Breakdown of the band-gap-common-cation rule: The origin of the small band gap of InN

It is well accepted that the band gap of a semiconductor compound increases as the atomic number decreases. However, recent measurements of the small band gap of InN (E(g)similar to0.9 eV) suggest that this rule may not hold for the common-cation In compounds. Using a band-structure method that includes band-gap correction, we systematically study the chemical trends of the band-gap variation in III-V semiconductors. The calculated InN band gap is 0.85+/-0.1 eV, much smaller than previous experimental value of similar to1.9 eV. The InN band-gap anomaly is explained in terms of atomic-orbital energies and the band-gap deformation potentials.