Interband absorption and the Γ‐point band structure parameters in HgSe

Optical absorption in HgSe crystals is measured in a wide energy range (0.04 to 0.9 eV). Transmission experiments are carried out at seven temperatures from 10 to 295 K. Very thin samples with electron concentration ranging from 4 × 10 17 to 2 ± 10 18 cm −3 at helium temperature are used (the absorption coefficient is measured up to 3 × 10 4 cm −1 ). Direct optical transitions Γ → Γ , manifesting themselves as a „step”︁ on the absorption curve, are observed at low temperatures. The relationship between the value of the negative energy gap E 0 and the value of the spin–orbit splitting Δ is determined from the energy of the front of the „step”︁ as a function of temperature. The absorption coefficient for HgSe is calculated numerically using Kane's formulae for the inverted band structure. The finite value of the spin–orbit splitting Δ and the parameters describing the interactions with „higher bands”︁ are taken into account. A new set of band structure parameters ( E 0 , d E 0 /d T , P , Δ, A ′, L ′, M , L – M – N ) is obtained. This set can explain the data measured as well as previous experimental results.