Electronic structure of wurtzite TlxIn1−xN alloys

The structural and electronic properties of wurtzite TlxIn1−xN materials have been investigated from first principles within the density functional theory (DFT). Band structures were obtained with the modified Becke-Johnson (MBJLDA) approach. A narrow band gap of 63 meV, induced by a strong spin-orbit coupling, is predicted in the hypothetical thallium nitride. The band gap inversion in TlN suggests that this compound is a promising candidate for a topological insulator. The lattice parameters of TlxIn1−xN alloys exhibit a linear behavior as a function of a Tl content x. An incorporation of Tl atoms in these systems leads also to a linear decrease of a band gap. For x>0.3 a very narrow energy gap, analogous to that of the pure TlN, is revealed. The band gap reduction of 26 meV/%Tl is comparable in value to those reported in the literature for dilute Bi-doped GaSb and InSb. The Tl-doped InN systems are promising materials for infrared optoelectronic devices.