Infrared Absorption in P-Type Semiconductors with Zincblende Structure –Application to Zinc Telluride–

Abstract

Infrared absorption in p -type semiconductors due to the transitions from split off valence bands to shallow acceptor states and to heavy and light hole bands was investigated in terms of k – π perturbation approach. Contrary to the case of germanium (diamond type), transitions from the split off valence bands to the top valence bands are allowed at \(\varGamma\) point in the zincblende structure. Although the contribution of the π matrix elements between \(\varGamma_{7v}\) and \(\varGamma_{8v}\) states to the absorption cross section is not large compared with that due to the k – π perturbed parts of wave functions in GaAs, they are of comparable magnitude in ZnTe. The radii of shallow acceptor states are determined to be 26 and 10 A respectively for Ge and ZnTe, by fitting the formulas derived here to experimental data. In the case of ZnTe, the change of absorption curve relative to photon energy with increasing temperature may be attributed to the increasing contributions of inter-valence band transitions.