Characterization of doped Bi₄Ge₃O₁₂ single crystals by light-induced absorption, electrical and photoelectrical measurements

Measurement of light-induced absorption changes, dark- and photoconductivity have been performed on Bi₄Ge₃O ₁₂ crystals doped with Fe, Rh and Fe+Rh. All samples exhibited a strong photochromic effect at room temperature, which was fully reversible after thermal annealing. It was found that Rh-doped Bi₄Ge ₃O₁₂ crystals possess a lower dark conductivity (σ_d = 5.2×10^-14 (Ωcm)^-1) at room temperature in comparison with other investigated samples. New centers in the Bi₄Ge₃O₁₂ inter-band structure, with thermal activation energies between 0.25 and 0.37 eV, have been created by doping with Fe and Rh. Fe-doped and Fe+Rh co-doped samples showed a non-linear photoconductivity dependence on light intensity, under illumination with a 514-nm laser.