Electronic structure of A narrow-band-gap semiconductor

We report calculations which show that the band structure of (Formula presented) is typical of a narrow-band-gap semiconductor. The gap is strongly dependent on the relative position of the Sb atoms inside the unit cell. We obtain a band gap of 0.22 eV after minimization of these positions. This value is more than four times larger than the result of a previous calculation, which reported that the energy bands near the Fermi surface are unusual. The electronic states close to the Fermi level are properly described by a two-band Kane model. The calculated effective masses and band gap are in excellent agreement with Shubnikov-de Haas and Hall effect measurements. Recent measurements of the transport coefficients of this compound can be understood assuming it is a narrow-band-gap semiconductor, in agreement with our results.