Steady-state photoconductivity in amorphous Ge₂Sb ₂Te₅ films

Steady-state photoconductivity measurements are carried out on thermally evaporated thin films of amorphous Ge₂Sb₂Te₅ samples in the temperature range between 323 and 243 K. The temperature dependence of the photoconductivity ensures the absence of the maximum normally observed in chalcogenides, and the photocurrent is thermally activated with activation energy slightly lower than that of the dark current value, 0.22+0.02 eV. The measured activation energies suggest recombination dominated by a trap states located at the equilibrium Fermi energy level. In the low temperature range another defect level corresponds to a deep electron trap carrier transport can be suggested which leads to low-temperature sensitisation of the photocurrent. The latter is evidenced from the γ values of approximately 1.0 in the Lux-Ampere characteristics.