Hot carrier dynamics in the satellite X valley and intervalley scattering in GaAs and AlGaAs

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:7232933

Wang, W

The time evolution of the population of hot electrons in the k 0 satellite X valley in GaAs and AlGaAs has been directly measured for the first time by a femtosecond visible-pump and IR-probe absorption spectroscopy. The L [yields] [Gamma] and X [yields] [Gamma] intervalley scattering was found to act as a source of heating of electrons in the [Gamma] valley. This enables determination of corresponding intervalley scattering rates from the measured carrier dynamics. The measured temporal and spectral profiles of the induced IR absorption have also been used to determine band structure parameters for GaAs and AlGaAs. The time-resolved IR absorption subsequent to the excitation at 527 nm in GaAs was measured. The rate equation analysis involving the intra-and-intervalley scattering are used to determine the X[sub 6] [yields] [Gamma][sub 6] intervalley scattering time. The transient X[sub 6] [yields] X[sub 7] band-to-band IR absorption spectrum in GaAs was measured by varying IR probe wavelengths, from which the energy gap between the minima of the X[sub 6] and X[sub 7] bands has been directly determined and the density of states effective mass for the X[sub 7] band has been found. The temperature dependence of hot electron relaxation in GaAs has been observed in a range from 4K to 300K. The time evolution of the population of hot electrons in the bottom of the X valley in Al[sub 0.6]Ga[sub 0.4]As was measured. Both phonon-assisted and alloy-disorder-induced intervalley scatterings were considered and the L[sub 6]-X[sub 6] intervalley deformation potential has been determined. The temporal profiles of the IR absorption for five Al[sub x]Ga[sub 1[minus]x]As samples were measured. The dynamics of the X valley electrons for samples with x [le] 0.408 was found to be different from that for samples with x [ge] 0.439. The critical value of x[sub c] which corresponds to direct-to-indirect band gap transition for Al[sub x]Ga[sub 1[minus]x]As was determined.

• Research Organization: City Univ. of New York, NY (United States)
• OSTI ID: 7232933
• Country of Publication: United States
• Language: English

Related Subjects

665400* -- Quantum Physics Aspects of Condensed Matter-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINIUM ARSENIDES
ALUMINIUM COMPOUNDS
ARSENIC COMPOUNDS
ARSENIDES
CHARGE CARRIERS
COUPLING
DYNAMICS
ELECTRON-PHONON COUPLING
ELECTRONIC STRUCTURE
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
GALLIUM ARSENIDES
GALLIUM COMPOUNDS
INFRARED SPECTRA
LEPTONS
MATERIALS
MECHANICS
PNICTIDES
SEMICONDUCTOR MATERIALS
SPECTRA
VISIBLE SPECTRA