The distribution function of photoexcited electrons in semiconductors subject to laser illumination

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Abstract
The steady-state form of the distribution function of electrons in the conduction band of a semiconductor, when the electrons are photoexcited from an impurity level by one or two monochromatic laser beams, is analysed for non-polar acoustic and for both non-polar and polar optical phonon scattering. A single laser line does not alter the Maxwellian distribution, but inverts the population near the band edge. Two laser lines induce non-Maxwellian elements into the distribution function whose character depends upon the laser bandwidths relative to the bandwidth for acoustic phonon scattering. Small bandwidths give rise to spikes in the distribution, but bandwidths comparable to the range of frequencies involved in acoustic phonon scattering may produce, in the absence of strong optical phonon scattering, profound deviations from the Maxwellian form. Numerical solutions of the Boltzmann equation for a few illustrative cases are presented.