TRAPS AND RECOMBINATION CENTERS IN PURE AND CO-DOPED BI12SIO20 CRYSTALS

Pure and Co-doped (0.36-1.8 mol% Co) Bi12SiO20 crystals have been stud ied. The temperature dependence of the dark and photoconductivity, the rmostimulated currents and the spectral dependence of the photoconduct ivity have been measured. Exponentially distributed traps situated clo se to the conduction band bottom have been found in pure BSO crystals. It was found that Co atoms act as donors in BSO crystals, and two new traps at about 0.24 and 0.45 eV appear. Based on the observed thermal quenching of the photocurrent an identical energy position of the ''s low'' recombination centers has been determined in both type of crysta ls. The defects responsible for the ''shoulder'' absorption (at about 2.7 eV below the conduction band) have been found to play the role of these ''slow'' recombination centers.