Spatial variation in carrier dynamics along a single CdSSe nanowire

- Femtosecond Kerr-gate microscopy allows ultrafast fluorescence measurements along different positions of a single nanowire.
- Amplified spontaneous emission observed at high fluences can be used to calculate recombination rates.
- Observation of ASE at different locations along a single CdSSe nanowire provides the ability to extract defect densities.

Ultrafast charge carrier dynamics along individual CdSxSe1−x nanowires has been measured. The use of an improved ultrafast Kerr-gated microscope allows for spatially resolved luminescence measurements along a single nanowire. Amplified spontaneous emission (ASE) was observed at high excitation fluences. Position dependent variations of ultrafast ASE dynamics were observed. SEM and colorimetric measurements showed that the difference in dynamics can be attributed to variations in non-radiative recombination rates along the wire. The dominant Shockley-Read recombination rate can be extracted from ASE dynamics and can be directly related to charge carrier mobility and defect density. Employing ASE as a probe for defect densities provides a new sub-micron spatially resolved, contactless method for measurements of charge carrier mobility.

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