Investigation of electrical and optical properties of Ge–Ga–As–S glasses doped with rare-earth ions

Bulk glasses Ge250Ga17As83S650 were prepared by direct synthesis from high purity (6 N) elements S, Ga, Ge, As and doped by rare earth (RE) elements — Pr, Dy, Nd, Sm or Ho. The DC and AC electrical conductivity were measured, and activation energies of relevant conductivity process were obtained from Arrhenius plots of its temperature dependence. The real part of complex permittivity as a function of temperature and frequency was deduced from AC conductivity data. Room temperature optical transmission and low temperature photoluminescence (PL) spectra were further investigated. The major feature in low-temperature PL spectra is the presence of the broad band luminescence of the base glass and relatively sharp 4f–4f radiative transitions due to the presence of RE3+ ions. When the broad band luminescence spectrally overlaps with 4f–4f transitions of RE3+ ions we can, in some cases, also observe the direct evidence of the energy transfer between the host glass and respective RE dopants which is manifested by the re-absorption of the base glass luminescence due to 4f–4f up-transitions.