Effect of sodium on the stationary dark and photoconductivity of amorphous Ge₃₀Se₇₀

Stationary dark and photoconductivity, and their temperature dependence, have been studied for Ge₃₀Se₇₀ bulk samples to which up to 0.8% of NaSe have been added. Strong increases in the dark conductivity and modest ones in the photoconductivity are observed. These increases are similar to the ones observed when pure germanium selenide films are deposited on Na-containing substrates. The photoconductivity increase is ascribed to sodium photosensitization, while the large, nearly temperature-independent contribution to the dark conductivity relates to hopping between highly conducting regions.