Effect of heat treatment on the Fermi energy and effective mass of n-type silicon germanium-gallium phosphide alloy

ABSTRACTA model is presented for the high temperature transport properties of large grain size, heavily doped p-type silicon-germanium alloys. Good agreement with experiment (±10%) is found by considering acoustic phonon and ionized impurity scattering for holes and phonon-phonon, point defect and hole-phonon scattering for phonons. Phonon scattering by holes is found to be substantially weaker than phonon scattering by electrons, which accounts for the larger thermal conductivity values of ptype silicon-germanium alloys compared to similarly doped n-type silicongermanium alloys. The relatively weak scattering of long-wavelength phonons by holes raises the possibility that p-type silicon-germanium alloys may be improved for thermoelectric applications by the addition of an additional phonon scattering mechanism which is effective on intermediate and long-wavelength phonons. Calculations indicate improvements in the thermoelectric figure of merit up to 40% may be possible by incorporating several volume percent of 20 Å radius inclusions into p-type silicon-germanium alloys.

Download Full-text

The propagation of electrons in a strained metallic lattice

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1953.0205 ◽

1953 ◽

Vol 220 (1143) ◽

pp. 542-561 ◽

Cited By ~ 103

Keyword(s):

Electrical Resistivity ◽

Effective Mass ◽

Fermi Energy ◽

Elastic Strain ◽

Perturbation Technique ◽

Deformation Potential ◽

Free Electrons ◽

Screw Dislocations ◽

Total Resistivity ◽

Ionic Lattice

The propagation of electrons in a strained metallic medium is studied by a perturbation technique in which the perturbing potential is proportional to the elastic strain and not, as in the usual treatment, to the displacement. For slowly varying strains the perturbing potential is a deformation potential of the type introduced by Bardeen & Shockley (1950), in which the periodicity of the lattice does not appear explicitly. In the approximation of nearly free electrons, the contribution of the ionic lattice to the deformation potential depends only on the dilatation and not on the shear components. This potential is modified by a flow of electrons from the compressed regions of the lattice to the expanded regions. The resulting potential depends only on the Fermi energy of the electrons and not on their interaction with the lattice of ions. In a higher approximation, the effective mass of the electrons depends on their interaction with the ionic lattice. The contribution of this term is comparable with that already considered, and the shear components of the strain also influence the deformation potential. The method is applied to estimate the electrical resistivity produced by dislocations of edge and screw types present in sodium and copper. In copper screw dislocations add appreciably to the total resistivity.

Download Full-text