Pavlova N. Non linear absorption of light and structure of energy states of a-ZnP2 single crystals.

The dissertation is devoted to experimental study of intrinsic and resonance two-photon absorption, band structure, deep local centers and complexes and generation-recombination processes in semiconducting ZnP2 crystals of tetragonal modification (a-ZnP2). There were studied undoped and doped with Ge, In and Se crystals of a-ZnP2. The resonant two-photon absorption in a-ZnP2 is studied in detail for the first time. In a-ZnP2 there were experimentally identified 12 critical points of the first order in conduction band and in valence band. There were identified 7 types of local centers in a-ZnP2 and 8 - in a-ZnP2:Ge; determined location depths of corresponding energy levels in band gap. The cross-section of absorption of Nd-laser radiation by impurities in a-ZnP2 is estimated. There were identified the defect centers, which provide real intermediate states of resonant two-photon absorption. The time of transverse relaxation of electrons in these centers is estimated. Study of influence of enlightment on induced absorption in a-ZnP2 is performed. With recursion method using tight-binding approximation there were calculated partial local densities of electronic states of ideal a-ZnP2 and that with natural defects.