UC Santa Barbara

Electron relaxation and transport dynamics in low-temperature-grown GaAs under 1 eV optical excitation was investigated by femtosecond transient transmission measurement and electro-optical sampling measurement in bulk samples and fabricated devices. An increase in the electron lifetime can be observed when the electron density is higher than 3x10(17) cm(-3). This effect is attributed to prolonged electron relaxation due to intervalley scattering of highly excited electrons and associated hot phonon effects. Our conclusion is further supported by bias-dependent studies where intervalley scattering was achieved using high electric fields. (C) 2003 American Institute of Physics.