PICOSECOND SPECTRAL HOLE-BURNING IN ZNCDTE LAYERS

The spectral and temporal behavior of absorption bleaching due to band - and state-filling processes in Cd1-xZnxTe polycrystalline layers wit h a nominal composition x=0.17 are investigated. The absorption bleach ing due to band-filling effects has a decay time in the range of 35 an d 90 ps which depends on the photon energies of the pump and test beam s. It is attributed to the relaxation of quasi-Fermi levels through th e bottom (top) of the conduction (valence) band and corresponds to the Lifetime of nonequilibrium charge carriers. The absorption bleaching due to state-filling processes corresponds to the nonthermal part of t he energy distribution of free carriers and therefore depends on the p hoton energy of the pump beam. A hole burning is found which peaks nea r the photon energy of the pump laser and which follows the temporal s hape of the laser pulses (20 ps). The asymmetry of the hole-burning sp ectrum is attributed to the energy dependence of the density of states which is important for electron-electron scattering processes. (C) 19 96 American Institute of Physics.