Semiconducting Lead Chalcogenides

Abstract

Yurii /saakovich Ravich was born in 1937 in the city of Pskov.ln 1959 he was graduated from the Physics Department of the Leningrad State University. He then joined the Institute of Semiconductors of the Academy of Sciences of the USSR, where he investigated the theory of photoelectric phenomena in semiconductors. At present, Ravich is a senior member of the scientific staff of the Institute. He is working on the band structura and carrier scattering mechanisms in semiconducting materials suitable for thermoelectric converters. Among his publications is a book on the "Photomagnetic Effect in Semiconductors and lts Applications."/a Anatol'evna Efimova was born in 1932 in Volgograd. After graduation from the Ural State University in 1954, she joined the Institute of Semiconductors. At present she is a senior member of the scientific staff of the Institute and is working on thermoelectric properties of semiconducting materials. /gor' Aleksandrovich Smirnov was born in 1932 in Leningrad. In 1955 he was graduated from the M. 1. Kalinin Leningrad Polytechnical Institute and promptly joined the Institute of Semiconductors, where he is now the head of the Laboratory for Thermal Phenomena. His major field of study is the thermal properties of solids. In 1964 Smirnov was awarded the A. F. loffe Prize for Solid State Physics. The original Russian text, published by Nauka Press in Moscow in 1968 as a pari of a series on "Physics of Semiconductors and Semiconducting Devices," has been corrected by the authors for this edition. The English translation is published under an agreement with Mezhdunarodnaya Kniga, the Soviet book export agency.

Chemical composition tuning in quaternary p-type Pb-chalcogenides – a promising strategy for enhanced thermoelectric performance

“…The valence band structure of lead chalcogenides (PbTe, PbSe and PbS) is described by a non-parabolic Kane band at the L point of the Brillouin zone (L band) and a parabolic band along the S line of the Brillouin zone (S-band). 28 Although the exact band structures of PbTe, 29 PbSe, 30 and PbS 31 have been suggested to be more complicated than the proposed model, they have been able to explain the transport properties of PbTe, 10 PbSe, 32 and PbTe-PbSe 4,33 very well. The energy gap, e g , at the L point is believed to linearly increase with the temperature by dE g /dT = 4 Â 10 À4 eV K À1 for all three chalcogenides.…”

“…A large total DOS can be due to either a large band degeneracy (N V ) or a high single-valley density of states effective mass of the degenerate valleys (m b *). 28,35 The density of states effective mass for PbS is shown to be larger than that for PbTe. 28 Therefore, the higher Seebeck coefficient of alloys containing sulphur (S5 and S10) in Fig.…”

“…28,35 The density of states effective mass for PbS is shown to be larger than that for PbTe. 28 Therefore, the higher Seebeck coefficient of alloys containing sulphur (S5 and S10) in Fig. 3(a) should be expected from the increase in the density of states.…”

“…The origin of the high Seebeck coefficient values over a wide temperature range is discussed based on the contributions of the two valence bands in p-type PbTe. 16,28 Results in the experimental literature show that the Seebeck coefficient of p-type PbTe deviates from the single band behaviour starting at a doping level in the mid-10 19 cm À3 range at room temperature, when carriers noticeably start to populate the heavy-hole band. 16,28 The band structure of PbTe is schematically shown in Fig.…”

“…The energy gap, e g , at the L point is believed to linearly increase with the temperature by dE g /dT = 4 Â 10 À4 eV K À1 for all three chalcogenides. 28 As the temperature rises, the energy of the light valence band is gradually reduced and reaches the S band edge. The density of states in the S band is much higher, and therefore, it provides a higher Seebeck coefficient than that with the L band alone, given the same carrier density.…”