Electron Spin Resonance of Photosensitive Fe3+ Centers in CdSe

ESR measurement has been carried out at X -band on isolated Fe 3+ (3d 5 , 6 S) in CdSe. The spin Hamiltonian parameters for Fe 3+ are estimated at 1.5°K as follows: g =2.043±0.002, a =(103±5)×10 -4 cm -1 , D =(602±3)×10 -4 cm -1 , and F =(-11±5)×10 -4 cm -1 . The influence of charge transfer from Fe 3+ to the surrounding ligands upon these parameters is discussed. Change of the valency of iron impurities caused by illumination is studied through the change of the intensity of Fe 3+ ESR signal. Following processes are elucidated. Light of 0.8 to 1.1 µ excites holes from Fe 3+ to the surrounding Se 2- ions; the excited holes are liberated thermally into the valence band. Light of about 7.4 µ excites electrons from Fe 2+ to the conduction band. Light of around 1.8 µ liberates holes from cadmium vacancies; a part of the liberated holes migrates through the valence band to Fe 2+ . Fe 3+ captures electrons from the conduction band, viz, acts as a recombination center for electrons.