First-principles calculations of electronic structures of new III-V semiconductors: Bx Ga1-x As and TlxGa 1-x As alloys

We investigate the electronic structures of new semiconductor alloys B xGa1-xAs and TlxGa1-xAs, employing first-principles calculations within the density-functional theory and the generalized gradient approximation. The calculation results indicate that alloying a small Tl content with GaAs will produce larger modifications of the band structures compared to B. A careful investigation of the internal lattice structure relaxation shows that significant bond-length relaxations takes place in both the alloys, and it turns out that difference between the band-gap bowing behaviours for B and Tl stems from the different impact of atomic relaxation on the electronic structure. The relaxed structure yields electronic-structure results, which are in good agreement with the experimental data. Finally, a comparison of formation enthalpies indicates that the production Tl xGa1-xAs with Tl concentration of at least 8% is possible. © 2008 Chinese Physical Society and IOP Publishing Ltd.