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Abrupt dependence of ultrafast extrinsic photoconductivity on er fraction in gaas:er



Elliott Brown, A. Mingardi, W-D. Zhang, Ari Feldman, Todd E. Harvey, Richard Mirin


We present a study of room-temperature, ultrafast photoconductivity associated with strong, sub-bandgap, resonant absorption around lamba} = 1550 nm in three MBE-grown GaAs epitaxial layers heavily doped with Er at concentrations of ≅2.9 x 1018 (control sample), 4.4 x 1020, and 8.8 x 1020 cm-3, respectively. Transmission-electron microscopy reveals a lack of nanoparticles in the control sample, but an abundance in the other two samples in the 1.0-to-3.0-nm-diameter range, consistent with the previously-known results. The novelty of the present work is demonstrating very high photoelectron (Hall) mobility (2.26x103 cm2/V-s) and terahertz power (46 υW average) in the 4.4 x 1020 sample, but then an abrupt decay in these properties as well as the dark resistivity as the Er doping is increased just 2 times. The Er doping has little effect on the picosecond-scale, 1550 nm photocarrier lifetime.
Applied Physics Letters


photoconductivity, rare-earth doped semiconductor, ultrafast materials


Brown, E. , Mingardi, A. , Zhang, W. , Feldman, A. , Harvey, T. and Mirin, R. (2017), Abrupt dependence of ultrafast extrinsic photoconductivity on er fraction in gaas:er, Applied Physics Letters, [online],, (Accessed June 14, 2024)


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Created June 30, 2017, Updated October 12, 2021