Excitonic and electronic transitions in Me–Sb(2)Se(3) structures

The optical anisotropy of the Sb(2)Se(3) crystals was investigated at 300 and 11 K. Excitonic features of four excitons (A, B, C, and D) were observed in the optical spectra of the Sb(2)Se(3) single crystals and in the photoelectric spectra of the Me–Sb(2)Se(3) structures. The exciton parameters, such as the ground (n = 1) and excited (n = 2) state positions and the binding energy (Ry), were determined. The effective mass of the electrons at the bottom of the conduction band (m(c)* = 0.67m(0)) as well as the holes at the four top valence bands (m(v1)* = 3.32m(0), m(v2)* = 3.83m(0), m(v3)* = 3.23m(0) and m(v4)* = 3.23m(0)) were calculated in the Г-point of the Brillouin zone. The magnitude of the valence band splitting V(1)–V(2) due to the spin–orbit interaction (Δ(so) = 35 meV) and the crystal field (Δ(cf) = 13 meV) were estimated in the Brillouin zone center. The energy splitting between the bands V(3)–V(4) was 191 meV. The identified features were discussed based on both the theoretically calculated energy band structure and the excitonic band symmetry in the Brillouin zone (k = 0) for crystals with an orthorhombic symmetry (Рnma). The photoelectric properties of the Me–Sb(2)S(3) structures were investigated in the spectral range 1–1.8 eV under E||c and E⟂c polarization conditions and at different applied voltages.