Noguera Becerra, Alejandro (1978) A theoretical study of the properties of photoexcited hot carriers in germanium. PhD thesis, University of Warwick.

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Abstract

This thesis is about a theoretical study of the properties of photoexcited holes in p-type Ge samples at low temperatures. The emphasis is on those carriers which are in non-equilibrium with the lattice. The energy distribution function for these carriers are obtained by a numerical solution of a rate equation which involves excitation, recombination and lattice scattering. Two models of a semiconductor are considered. The complicated band structure of p-type Ge is first approximated by a parabolic heavy hole band; later developments make necessary the inclusion of a parabolic light hole band.

Two types of photoexcitation are analysed. In the first, carriers are generated by a narrow spectrum of photoexcitation and the distribution function is studied as function of the initial excitation energy, the spectrum bandwidth and the density of the compensating impurities. For a very narrow excitation spectrum, the distribution of carriers exhibits a series of equally spaced peaks at carrier wavevectors equal to and below the photoexcitation wavevector. At compensation densities greater than or about equal to 10¹³ cm-³ and photoexcitation energies about 30 meV the distribution function resembles a Maxwellian function with carriers temperature much greater than that of the lattice.

The second excitation spectrum involves room temperature black- body radiation. In the one band model, the distribution function is, for Cu-doped Ge with compensation densities less than or equal to 10¹³ cm-³) nearly a Maxwellian function with the carrier temperature obtained from an energy balance equation. Good agreement with experimental mobility data is found for the same compensation densities. For higher compensation densities a parabolic light hole band is then included in the model of semiconductor and the experimental photohall mobility data for Cu-and Ga-doped Ge samples are used to deduce a value for the deformation potential a. This parameter is found to depend on both the compensation density and lattice temperature.

It is also reported additional calculations which suggest ways to improve the theoretical model.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QC Physics Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Germanium, Hot carriers, Photons, Photoelectrochemistry, Photoabsorption
Official Date:	March 1978
Dates:	Date Event March 1978 Submitted
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Hearn, C. J.
Sponsors:	Universidad de los Andes (Mérida, Venezuela)
Extent:	iv, 129 leaves : illustrations, charts
Language:	eng

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