Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 26: Ultra-fast phenomena

HL 26.5: Talk

Wednesday, March 14, 2018, 10:30–10:45, EW 202

Electron mobility and lifetime in GaAs/In_xGa_1−xAs core/shell nanowires studied by optical pump – THz probe spectroscopy — •Ivan Fotev^1,2, Leila Balaghi^1,2, René Hübner¹, Johannes Schmidt¹, Markus Hähnel¹, Harald Schneider¹, Manfred Helm^1,2, Emmanouil Dimakis¹, and Alexej Pashkin¹ — ¹Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany — ²TU Dresden, Germany

We utilize ultrafast optical pump – terahertz probe spectroscopy in order to investigate charge carrier response of GaAs/In_xGa_1−xAs core/shell nanowires (NWs) produced by molecular beam epitaxy. The NWs were ≈2 µm long. The GaAs core diameter was 25 nm and the InGaAs shell thickness was 80 nm. We studied the shells with different compositions, from x=0.20 to x=0.44.

From the pump-probe measurements we extracted terahertz photoconductivity of NWs and used the localized surface plasmon model to fit the results. The charge carrier lifetimes were estimated to be around 80–100 ps while the extracted electron mobilities reach 3700 cm²V⁻¹s⁻¹ at room temperature. Even without a surface passivation shell, these values are higher than those in previously studied GaAs/AlGaAs core/shell nanowires, but still lower than the ones for bulk InGaAs. Possible reasons (sources of electron scattering) which affect the mobility will be discussed.