Photoconductivity and carrier lifetime in In/Bi doped GeSe glasses

Photoconducting properties of the GexSe100-x bulk semiconducting glass syst em are found to improve with the addition of indium or bismuth. In the GexI n5Se95-x system, appreciable variations in photoconductivity and carrier li fetime are found to occur at average atomic coordination numbers Z = 2.41 a nd 2.73. These are explained on the basis of the mechanical threshold and c hemically ordered covalent network (COCN) models. In the Ge20BixSe80-x syst em, a sharp decrease in photoconductivity and carrier lifetime are observed at the composition corresponding to x = 7 (Z = 2.47), where a p-type to n- type transition has been reported earlier. Although differences in many of their properties do exist, Ge-Se, Ge-In-Se and Ge-Bi-Se systems remain type I photoconductors and their behaviour can be analysed in terms of the ABFH model.