Effect of Copper Doping on the Optical Properties of AgxGaxGe1 − xSe2 (0.12 ≤ x ≤ 0.25) Single Crystals

Single crystals of AgGaSe2-GeSe2 γ-solid solutions are investigated. The AgxGaxGe1 − xSe2 (0.12 ≤ x ≤ 0.25) solid solutions are anisotropic p-type semiconductors with a 290-K band gap of about 0.26 eV. The high defect density in the crystals results in static disordering and the formation of density-of-states tails in the band gap, reducing their transmittance. Cu doping leads to bleaching in the optical window of the crystals (visible through near-IR spectral region). A model is proposed for the interaction between the dopant atoms and structural defects in the crystals. The radiation hardness and laser damage threshold of AgxGaxGe1 − xSe2 are evaluated.