Reversible and irreversible resistance changes for gamma-ray irradiation in silver-diffused germanium telluride

We report on the irreversible and reversible resistance changes for γ-ray irradiation in amorphous GeTe thin films with Ag electrodes. The γ-ray irradiation at a dose of 1 kGy irreversibly decreased the DC resistance by two orders of magnitude. The irreversible resistance change was caused by the formation of a conductive region that consisted of Ag-Te compounds. In-situ real-time DC resistance and AC impedance measurements revealed reversible variations in several electrode structures with DC resistances ranging widely from about 10 kΩ to about 5 MΩ. The DC resistance decreased by 2–5% with a time constant of about 3–7 min following the γ-ray irradiation with a dose rate of 0.5–2 kGy/h, and recovered on interruption. The AC impedance measurement was analyzed with a simple equivalent circuit consisting of a parallel RC circuit of the Ag-diffused GeTe matrix, connected serially to the interface resistance. The interface resistance and the capacitance of the matrix exhibited a fast reversible variation, which is explained by trapping and detrapping of carriers in the charged defects formed by the Ag re-diffusion. The resistance of the matrix showed a slow reversible variation with a time constant of 7 min, similar to the DC resistance. The slow reversible variation is attributed to the growth and dissolution of the conductive region caused by the Ag re-diffusion.