Direct imaging of electron recombination and transport on a semiconductor surface by femtosecond time-resolved photoemission electron microscopy

Much effort has been devoted to the development of techniques to probe carrier dynamics, which govern many semiconductor device characteristics. We report direct imaging of electron dynamics on semiconductor surfaces by time-resolved photoemission electron microscopy using femtosecond laser pulses. The experiments utilized a variable-repetition-rate femtosecond laser system to suppress sample charging problems. The recombination of photogenerated electrons and the lateral motion of the electrons driven by an external electric field on a GaAs surface were visualized. The mobility was estimated from a linear relationship between the drift velocity and the potential gradient.