Ultrafast upper satellite valley spectroscopic dynamics using UV-pump IR-probe absorption spectroscopy in GaAs and GaP

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Abstract
Energy relaxation of electrons in the X6 and X7, satellite, X6 (reversible reaction) (Gamma) and X7 (reversible reaction) (Gamma) , have been investigated using time-resolved UV pump-IR probe absorption spectroscopy in GaAs and GaP. Energy band renormalization of the X6 and X7 valleys, band filling effects in the X6 yields X7 spectra, and O.D. spectral relaxation of electrons in the X6 and X7 valleys by intervalley scattering, X6 (reversible reaction) (Gamma) and X7 (reversible reaction) (Gamma) , were all observed as a function of photoexcited electron density. From the observed energy relaxation dynamics it is determined that X7 yields (Gamma) intervalley scattering is faster than X6 yields (Gamma) intervalley scattering in GaAs. These experiments were performed by measuring the absorption spectra of 500-fs IR probe pulses induced by 500-fs UV pump pulses, as a function of delay time and pump pulse fluence. The spectra, at different pump pulse fluences and pump-probe delay times, are interpreted in terms of free carrier absorption, X6 yields X7 direct interconduction band absorption, and indirect interconduction band absorption.

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