Electronic structures and doping of InN, InxGa1−xN, and InxAl1−xN

Abstract

The electronic structures of InN, ${\mathrm{In}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$N, and ${\mathrm{In}}_{\mathrm{x}}$ ${\mathrm{Al}}_{1\mathrm{-}\mathrm{x}}$N are predicted and these materials are found to be direct-band-gap semiconductors with fundamental band gaps ranging from orange through the blue-green to the ultraviolet. The deep levels associated with substitutional s- and p-bonded impurities are predicted, and, for InN we find (i) that the native defect responsible for naturally occurring n-type InN is a nitrogen vacancy (not ${\mathrm{N}}_{\mathrm{In}}$); (ii) that the nitrogen vacancy also produces a deep level just below the conduction-band edge, which is responsible for an observed 0.2-eV optical-absorption feature; (iii) that p-type doping should be achievable by inserting column-II impurities on In sites; (iv) that n-type conductivity should result from oxygen atoms on N sites; (v) that ${\mathrm{In}}_{\mathrm{N}}$ produces s- and p-like deep levels near midgap that are responsible for an optical-absorption feature near 1 eV; (vi) that column-IV impurities on either anion or cation sites will tend to make the material semi-insulating, and (vii) that an isoelectronic electron trap should be produced by ${\mathrm{B}}_{\mathrm{In}}$, whereas column-V impurities on the N site should produce deep isoelectronic hole traps. Similar results hold for the alloys ${\mathrm{In}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$N and ${\mathrm{In}}_{\mathrm{x}}$ ${\mathrm{Al}}_{1\mathrm{-}\mathrm{x}}$N. Some impurities undergo shallow-deep transitions in the alloys, as functions of alloy composition.