Electronic effects of sodium in epitaxial CuIn_1-xGa_xSe₂

Temperature dependent Hall effect measurements were made on Na-contaminated and uncontaminated epitaxial p-type CuIn_1-xGa_xSe₂ films. Na was introduced by diffusion into as-deposited samples using both NaOH and Na₂Se as sources. Na concentrations were measured using secondary ion mass spectroscopy by comparison to an implanted standard. Films contaminated with Na from either source were found to have much lower compensating donor densities than as-deposited films. Oxygen and other impurities were not found to be necessary to produce this effect although some changes with Se content were observed. These were independent of the Na effect.