Direct and simultaneous observation of ultrafast electron and hole dynamics in germanium.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28569752.
- Also identified by DOI 10.1038/ncomms15734 and PMC identifier 5461502.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Understanding excited carrier dynamics in semiconductors is crucial for the development of photovoltaics and efficient photonic devices. However, overlapping spectral features in optical pump-probe spectroscopy often render assignments of separate electron and hole carrier dynamics ambiguous. Here, ultrafast electron and hole dynamics in germanium nanocrystalline thin films are directly and simultaneously observed by ultrafast transient absorption spectroscopy in the extreme ultraviolet at the germanium M<sub>4,5</sub> edge. We decompose the spectra into contributions of electronic state blocking and photo-induced band shifts at a carrier density of 8 × 10<sup>20</sup> cm<sup>-3</sup>. Separate electron and hole relaxation times are observed as a function of hot carrier energies. A first-order electron and hole decay of ∼1 ps suggests a Shockley-Read-Hall recombination mechanism. The simultaneous observation of electrons and holes with extreme ultraviolet transient absorption spectroscopy paves the way for investigating few- to sub-femtosecond dynamics of both holes and electrons in complex semiconductor materials and across junctions.