  Structural and electronic properties of hypothetical zinc blende
Tl(x)Ga(1-x)N alloys have been investigated from first principles. The
structural relaxation, preformed within the LDA approach, leads to a linear
dependence of the lattice parameter a on the Tl content x. In turn, band
structures obtained by MBJLDA calculations are significantly different from the
corresponding LDA results. The decrease of the band-gap in Tl-doped GaN
materials (for x<0.25) is predicted to be a linear function of x, i.e. 0.08 eV
per atomic % of thallium. The semimetallic character is expected for materials
with x>0.5. The obtained spin-orbit coupling driven splitting between the
heavy-hole and split-off band at the Gamma point of the Brillouin zone in
Tl(x)Ga(1-x)N systems is significantly weaker when compared to that of Tl-doped
InN materials.
