The thermally stimulated current and photoconductivity behaviors were studied as a function of temperature and light intensity in n-type single crystals which had been doped with Cl. Thermally stimulated current measurements were performed at temperatures ranging from 80 to 450K. An electron trapping center at about 0.38eV below the conduction band, and an electron capture cross-section of 8 x 10-18cm2 were deduced. Re-trapping was negligible in this center. A marked thermal quenching of the photo-current was observed at various excitation levels. The results were analyzed by using a simple kinetic model which took account of 2 different types of center. In this way, a hole center at about 0.20eV above the valence band was detected.

G.Micocci, A.Serra, A.Tepore: Journal of Applied Physics, 1997, 81[9], 6200-4