Deep Centers Influence On Photoresponse Characteristics In High-Resistivity ZnSe

Abstract

The photocurrent peak after preliminary optical excitation with specific wavelength in high resistivity (ρ≍1012 Ω∗cm), unintentionally doped ZnSe monocrystals was observed. To study photocurrent “flash” phenomenon, the photocurrent relaxation spectra, photon-capture crosssection (PCCS) spectra and photo-electron paramagnetic resonance (photo-EPR) were investigated. Two-levels model involving the recombination of an S-center and an acceptor A has been developed to obtain the relation between recombination probability and instantaneous photocurrent value. The S-centers ionization energies (1.06eV and 1.14eV from the bottom of the conduction band) and charge carriers life times were determined. The acceptor's positions in ZnSe band gap are equal to 2.05, 2.11, 2.16 and 2.21eV from the bottom of the conduction band. The photocurrent and PCCS “flash” nature as well as complicated photo-EPR are associated with the relaxation of S-centers attributed to Fe ion in the band gap of semi-insulated ZnSe.