Picosecond transient Rayleigh scattering spectroscopy: probing band structure and carrier dynamics of single semiconductor nanowires

We present picosecond pump-probe measurements of Rayleigh scattering from GaAs nanowires which show that these differential spectra are sensitive indicators of both the density and temperature of electron-hole pairs in a single nanowire. The probe pulse measures the change in the Rayleigh scattering as a function of time after excitation by the pump pulse. Because the Rayleigh scattered signal depends sensitively on both the real and imaginary parts of the dielectric response, these measurements provide direct insight into the nonlinear changes induced by both many body effects and state filling. Measurements on high quality single core-shell GaAs/AlGaAs nanowires were carried out at low temperature. Maps of the differential Rayleigh scattering spectra as a function of time are generated and interpreted using a semi-phenomenological model of these nonlinear effects. We show that both the photoexcited carrier density and the carrier temperature as a function of time can be directly obtained from the transient Rayleigh scattering data.