The fundamental absorption edge in MnIn₂Se₄ layer semi-magnetic semiconductor

From the study of the optical absorption coefficient and photoluminescence spectra of the layer semi-magnetic semiconductor MnIn₂Se₄ the nature of its fundamental absorption edge is established. It is found that the lowest-energy-gap of this compound is allowed-indirect between parabolic bands that vary from about 1.55–1.43 eV in the temperature range from 10 K to room temperature. In addition, two allowed direct band-to-band transitions beginning at 1.72 and 1.85 eV at 295 K, and at 1.82 and 1.96 eV at 10 K which are related to optical absorption processes between the uppermost Γ₄(z) and the middle Γ₅(x) valence bands and the conduction band respectively, are observed in the high energy range. It is also found that the crystal field splitting parameter (Δ_cf) of MnIn₂Se₄ is of about 0.15 eV nearly independent of the temperature. At energies around 2.2 eV a photoluminescence band related to internal transitions between d-excited levels of Mn⁺² ion to its ⁶A₁ ground state is also observed in spectra.