Electrical and optical properties of binary glasses from the arsenictelluriumselenium system

Abstract

An investigation of binary glasses derived from the arsenicseleniumtellurium system is described in which measurements were made of d.c. conductivity over a range of temperatures, space charge limited current, density and absorption in the near infrared region. For the higher temperature region the electrical results were consistent with conduction being due to carriers excited into extended states. While conduction at lower temperatures may in some cases be due to carriers hopping in localized states at the band edges, an alternative approach in which the localized states were considered to act as donors and acceptors gave satisfactory agreement with the experimentally determined conductivity versus temperature and activation energy versus temperature relationships and with the value of the pre-exponental constant in the conductivity expression. An anomalous field dependence of conductivity was found for annealed specimens of two glasses and it is tentatively suggested that this is associated with the creation of an impurity band. Measurements of space charge limited current showed that gold gave ohmic contacts to the glass, whereas silver and copper did not. The measurements also provided evidence for the localized states having an exponential distribution. Changes of electrical properties and density as a function of glass composition are discussed in the light of possible structural changes taking place in the glasses. The absorption edges of the glasses in the infrared region were found to be exponential in form and had slopes that did not very greatly for the range of compositions studied.