Discrimination between energy transfer and back transfer processes for GaAs host and Er luminescent dopants using electric response analysis

Abstract

The energy transfer and back transfer processes of GaAs co-doped with Er and O (GaAs:Er,O) were experimentally distinguished by using a frequency response analysis of the AC photocurrent. The results were achieved by using the difference in the frequency dispersion between (1) the dispersion of the energy transfer, which is triggered by the trapping of free charges in the GaAs host and is represented with the Debye relaxation response and (2) the dispersion of the energy back transfer, which is induced by non-radiative transition of 4f bound electrons in the Er dopants and is described with a Lorentzian. The Debye relaxation response found in GaAs:Er,O provided a charge trapping time that was dependent on temperature, which was well correlated with the thermal quenching property of intense intra-4f-shell luminescence. The spectral shape of the Lorentzian dependence on the temperature was explained with the thermal excitation of Er 4f electrons and release of trapped charges in GaAs. The thermal excitation and release of charges consistently explained the characteristics of weak 4f luminescence in low- and high-temperature regions, respectively.