Ultrafast charge carrier dynamics at semiconductor material interfaces

Dr. Mihai Vaida – University of California Berkeley

Understanding ultrafast photoinduced charge carrier dynamics at semiconductor material interfaces can guide advances in the next generation of catalysts to produce storable fuels from sustainable inputs as well as to develop high efficiency solar cells. Time resolution, surface sensitivity, and element specificity are technical ingredients required to investigate ultrafast photoinduced processes of charge transfer and charge localization at semiconductor surfaces. All these requirements are fulfilled by means of core-level photoemission spectroscopy using tunable femtosecond extreme ultraviolet laser pulses.

This talk emphasizes the investigation of ultrafast charge carrier dynamics at three different interfaces, i.e. semiconductor-gas phase, semiconductor-metal, and semiconductor-semiconductor, by monitoring the full suite of steps from charge excitation to charge separation and subsequent charge recombination. In the particular case of a semiconductor-semiconductor interface, the electronic structure of a thin semiconducting film attached to a dissimilar semiconductor was manipulated to form a type II heterostructure that exhibits important electrical properties, allowing a selective separation of charges.