Anisotropic picosecond photoconductivity caused by optical alignment of electron momenta in cubic semiconductors

Transient photoconductivity in cubic semiconductors InGaAs and InAs excited by a femtosecond laser pulse in the presence of a uniform dc electric field has been studied with the use of the Monte Carlo simulation by taking into account optical alignment of photoexcited electrons over their momenta. S...

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Bibliographic Details
Published in:Journal of applied physics 2014-02, Vol.115 (7)
Main Authors: Malevich, Y. V., Adomavičius, R., Krotkus, A., Malevich, V. L.
Format: Article
Language:English
Subjects:
Alignment
ANISOTROPY
Applied physics
Computer simulation
COMPUTERIZED SIMULATION
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
CRYSTAL STRUCTURE
Crystallography
Dependence
ELECTRIC FIELDS
ELECTRON MOBILITY
ELECTRONS
ENERGY DEPENDENCE
EXCITATION
Femtosecond pulses
GALLIUM ARSENIDES
INDIUM ARSENIDES
Indium gallium arsenides
LASER RADIATION
MONTE CARLO METHOD
Monte Carlo simulation
PHOTOCONDUCTIVITY
Photoelectric effect
Photoelectric emission
POLARIZATION
Pulse amplitude
SEMICONDUCTOR MATERIALS
Semiconductors
THRESHOLD ENERGY
Transient photoconductivity
TRANSIENTS
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Summary:Transient photoconductivity in cubic semiconductors InGaAs and InAs excited by a femtosecond laser pulse in the presence of a uniform dc electric field has been studied with the use of the Monte Carlo simulation by taking into account optical alignment of photoexcited electrons over their momenta. Simulations show that due to the optical alignment effect and energy dependence of the electron mobility, the transient photoconductivity in cubic semiconductors becomes anisotropic during the first few picoseconds after optical excitation. The magnitude of this anisotropy reaches its peak when the excess energy of the optically excited electrons approaches the threshold for the intervalley transfer. It has also been found that when the electrons are excited near the threshold energy for the intervalley transfer, the component of the transient photocurrent directed along the dc field for a short time after the end of the femtosecond optical pulse can become negative. The anisotropy of the transient photoconductivity has been investigated experimentally on (001) InGaAs sample by the optical pump - terahertz-probe technique. Optically induced changes in terahertz pulse amplitude were found to be dependent on the direction of terahertz field relative to the polarization of the optical pump pulse and to the crystallographic axes of the semiconductor. Experimental data have been explained in terms of the transient anisotropic photoconductivity and correlate with the results of the Monte Carlo simulation.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4865961