Intervalley separation in the conduction band of InGaAs measured by terahertz excitation spectroscopy

Abstract

Spectral dependencies of terahertz radiation from the femtosecond laser-illuminated surfaces of GaxIn1−xAs (x=1, 0.8, and 0.47) have been investigated experimentally at high optical fluencies and laser wavelengths ranging from 600 to 800 nm. The terahertz pulse amplitude increased with the increasing laser photon energy due to larger excess energies of photoexcited electrons and more efficient spatial separation of electrons and holes at the illuminated surface. This increase was stopped with the onset of electron transitions to subsidiary conduction band valleys. Analysis of these experiments was used for evaluating the energy positions of the X and L conduction band valleys in GaxIn1−xAs alloys as a function of their composition.