Evidence of coulomb interaction at the e1 interband transition of hexagonal CdSe

Transmission and reflection spectra are measured on CdSe single crystals in the region 3.6 to 5.9 eV at 109 K and RT and the absorption coefficient, refractive index, and real and imaginary part of the DF are calculated from these data. The line shape of ϵ2 around the E1(B) peak indicates a strong influence of electron–hole interaction. A comparison with Kane's theory gives a binding energy of the two‐dimensional exciton of 0.23 eV. In thermally modulated transmission spectra a new structure is observed which is attributed to the M1 edge of the E1(A2) exciton yielding a binding energy of the same magnitude.