Electronic Structures and Optical Properties of Ga-Rich In_<i>x</i>Ga_1−<i>x</i>N Nanotubes

The electronic structures and optical properties of single-walled Ga-rich zigzag InxGa1−xN nanotubes (NTs) are investigated using first-principles calculations. We find that In atoms substitute Ga atoms randomly in InxGa1−xN NTs, in which some typical In−N clusters, chains, and rings are embedded by chance. Both the electronic structures and optical properties insensitively depends on In distribution. A spiculate density of states (DOS) peak appears in the vicinity of the valence band maximum (VBM) and conduction band minimum. The imaginary part ε2 of the complex dielectric function has also a sharp peak related to the band edge absorption. The In doping can effectively adjust the band gap and enhance the peak of the band edge absorption and DOS. Unlike bulk InxGa1−xN alloys, the electron states at the VBM become extended for the NTs with various In distributions.