Spectral dependence of anisotropic picosecond photoconductivity in cubic semiconductors

The "optical pump-terahertz probe" technique is used to investigate the spectral dependence of the anisotropic picosecond photoconductivity in an InGaAs cubic semiconductor excited by femtosecond laser pulses. It is shown that the anisotropy of the photoconductivity, which is caused by the alignment of the momenta of photoexcited charge carriers and by the energy dependence of the carrier mobility, depends nonmonotonically on the photon energy of the optical pump radiation and attains a maximum when the energy of pump photons is in the vicinity of the threshold for the onset of electron transitions to the subsidiary valleys in the conduction band.