Regulation of corundum band gap width by p elements and vacancy co-doping

Abstract

The coherent potential approximation is applied to study the evolution of the electronic structure mainly in the vicinity of the energy gap of pure corundum (α-Al2O3) in dependence on p cation and anion impurities (Si, Ge, Sn, C, and N) and aluminum/oxygen deficiency. The study shows an energy gap reduction due to appearance of new impurity/vacancy peaks at the edges of the energy gap of undoped α-Al2O3, which agrees with experiments for some single impurities. Simultaneously doping with p elements and vacancies of α-Al2O3-based compounds Al2{O2.88C0.06}, {Al1.94Si0.03Ge0.03}{O2.88C0.03N0.06}, and {Al1.90Si0.03Ge0.03Sn0.03}{O2.88C0.03N0.06} with the 1.9 eV energy gap are proposed as new effective materials for applications in photocatalysis and photovoltaic and optical devices.