IMPROVEMENT OF CHARGE-TRANSPORT IN SE-AS GLASSES BY DOPING WITH HALOGENS

Carrier drift mobility and dc conductivity have been measured as functions of dopant concentration for Se-As glasses containing 2-10% As, doped with I, Br or Cl. It was established that concentration dependences of the carrier drift mobility and conductivity have maxima for concentration of Cl or Br between 10 and 100 ppm. A significant increase in the carrier drift mobility was observed for doped samples. Depending upon the dopant species, the increase varied from one to four orders of magnitude. The increase in dc conductivity, corresponding to the drift mobility maximum, was no more than one order of magnitude. The analysis of experimental data indicates that the effects observed can be attributed to changes in the concentration of charged intrinsic defects due to the influence of halogen impurities on these defects. The halogen impurities are incorporated into the glasses in two ways: (1) as negatively charged centres and (2) as chemically active atoms forming neutral bonding configurations. In the latter case, a decrease in the concentrations of both negatively and positively charged intrinsic defects is observed.