WAVELENGTH-DEPENDENT EFFECTIVE TRAP DENSITY IN CDTE - EVIDENCE FOR THE PRESENCE OF 2 PHOTOREFRACTIVE SPECIES

An accurate determination of the effective trap density in CdTe:V is p erformed using both counter-propagating (small grating spacing) and co -propagating (large grating spacing) two-wave mixing. This enhanced pr ecision allows to show a variation of the effective trap density with wavelength. We show that such a change is explained when two traps bot h coupled to the conduction and the valence bands are present. New the oretical expressions for the electron-hole competition coefficient and Debye screening length are derived and used.