α-Ag₂Se as a Degenerate Semiconductor

Abstract

The electron concentration n in α Ag 2 Se (high temperature phase) is varied from 0.6 to 6×10 19 cm -3 by sending a current across the galvanic cell Ag | AgI | Ag 2 Se specimen | Pt. The electron gas in the specimen is fairly highly degenerate. The surface potential V , the electrical conductivity σ, the Hall coefficient R , the thermoelectric power \(\varTheta\), the Nernst coefficient Q , other transport coefficients, and the magnetic susceptibility, etc. are measured as functions of the electromotive force E of the cell, as n is varied. The fact that d V / d E is nearly unity shows that E represents the relative height of the Fermi level. We notice the discrepancies between \(\varTheta e/k\) and \(\frac{1}{3}\pi^{2}\partial\log\sigma/\partial(eE/kT)\) and between Q e / k and \(\frac{1}{3}\pi^{2}\partial(R\sigma)/\partial(eE/kT)\) which suggest that the conduction band is not rigid. Taking these discrepancies into consideration, the experimental data are analized with the formal theory of the degenerate electron gas under the spherical band model. The analyses show that the data are almost consistent with the picture; the effective mass increases with increasing electron energy (non-parabolic band) and also increases with excess Ag content, while the relaxation time is nearly constant.