Photoacoustic Spectroscopic Study of Optical Band Gap of Zn1-xBexSe Semiconductors

Using the photoacoustic spectroscopic (PAS) technique for the first time, the composition-dependent optical absorption coefficient and band gap of Zn1−xBexSe semiconductors (with x=0.0–0.25) have been measured at room temperature. The band gap E0 estimated from the PAS spectra varies nonlinearly with Be concentration. The exchange iInteraction of electrons in conduction and valence bands, effects of polytypes, microstructures, and the mixed crystallization (zinc-blend and wurtzite structures) effect are considered for the analysis of the data. The observed exponential edge (Urbach’s edge) can be considered as an iInternal Franz–Keldish effect arising from the charged impurity generated and “frozen-in” optical phonon-generated fields. The phonon- assisted indirect transition at the band tail regions for some samples is also observed in the present studies.