On the Fundamental Energy Gap in GeTe

Korzhuev, M. A.

doi:10.1002/pssb.2221120149

Cited by 15 publications

(10 citation statements)

References 6 publications

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“…The calculated band structures for GeTe are consistent with those in the available literature. [71][72][73][74][75][76][77][78][79] It is seen Figure 4 Temperature-dependent Seebeck coefficient and resistivity for Bi x Ge 1 − x Te with x = 0.075 (n H = 1.37 × 10 20 cm − 3 ) showing a transition from conduction by the Σ band in α-GeTe at To~550 K to that by both the L and Σ bands in β-GeTe at T4~625 K due to the phase transition. The insets show that the Fermi surface evolution is related to the transition.…”

Section: Resultsmentioning

confidence: 99%

Electronic origin of the high thermoelectric performance of GeTe among the p-type group IV monotellurides

et al. 2017

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PbTe and SnTe in their p-type forms have long been considered high-performance thermoelectrics, and both of them largely rely on two valence bands (the first band at L point and the second one along the Σ line) participating in the transport properties. This work focuses on the thermoelectric transport properties inherent to p-type GeTe, a member of the group IV monotellurides that is relatively less studied. Approximately 50 GeTe samples have been synthesized with different carrier concentrations spanning from 1 to 20 × 10 20 cm − 3 , enabling an insightful understanding of the electronic transport and a full carrier concentration optimization for the thermoelectric performance. When all of these three monotellurides (PbTe, SnTe and GeTe) are fully optimized in their p-type forms, GeTe shows the highest thermoelectric figure of merit (zT up to 1.8). This is due to its superior electronic performance, originating from the highly degenerated Σ band at the band edge in the low-temperature rhombohedral phase and the smallest effective masses for both the L and Σ bands in the high-temperature cubic phase. The high thermoelectric performance of GeTe that is induced by its unique electronic structure not only provides a reference substance for understanding existing research on GeTe but also opens new possibilities for the further improvement of the thermoelectric performance of this material.

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Section: Resultsmentioning

confidence: 99%

Electronic origin of the high thermoelectric performance of GeTe among the p-type group IV monotellurides

et al. 2017

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“…The width of the band gap of Cu 2 Se is Eg = 1.25 eV according to [21], the optical width of the band gap depends on the copper content in the phase and is 1.1, 1.6 and 1.7 eV for Cu 2 Se , Cu 1.84 Se , and Cu 1.82 Se , respectively [46]. At high temperatures in Cu 2−σ Se , the average free path of holes does not exceed the lattice period [47]. Lithium most likely acting as monovalent donor impurity at the substitution of copper Cu 2−σ Se , and thus, Li 0.10 Cu 1.75 Se compositions must be partially compensated semiconductors, and the composition Li 0.25 Cu 1.75 Se must be fully compensated semiconductor.…”

Section: Resultsmentioning

confidence: 99%

Effect of lithium doping on electrophysical and diffusion proper-ties of nonstoichiometric superionic copper selenide Cu1.75Se

Balapanov¹,

Kuterbekov²,

Kubenova³

et al. 2017

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The results of studies of the ionic conductivity and the conjugated chemical diffusion coefficients (CCDC) in the nonstoichiometric Li x Cu 1.75 Se (0 ≤ x ≤ 0.25) ternary alloys are presented. It has been observed that the values of the ionic conductivity of Cu 1.75 Se copper selenide decreases with lithium doping in general owing to increasing the the activation energy. The increasing of the conjugate chemical diffusion coefficients of the cations and electron holes was observed with increasing of lithium content, despite the decreasing of self-diffusion coefficients of the cations and decreasing of electron mobilities. The behavior of the conjugate chemical diffusion coefficients explained by a decrease in the degree of non-stoichiometry of the composition, leading to an increase of the internal electric field accelerating the motion of slower particles.

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“…The reason for the rapid increase of the thermoelectric figure of merit with temperature becomes clearer if we take into account the changes in the band structure with temperature discussed above and from the temperature dependence of the fundamental energy gap for GeTe [14] and the investigated solid solutions [15]. They are three facts: (i) The temperature coefficient of changes of the fundamental gap for the Fig.…”

Section: Discussionmentioning

confidence: 94%

Thermoelectric figure of merit of the system (GeTe)1−x(AgSbTe2)x

Placheova¹

1984

Phys. Stat. Sol. (a)

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The thermoelectric properties of polycrystalline samples of GeTe-rich side solid solutions (GeTe)l -, .. (AgSbTe,), for the compositions z = 0.00, 0.10, 0.15, 0.20, and 0.29 are investigated. The temperature dependences of the Seebeck coefficient and the electrical resistivity and the dependences of the total thermal conductivity a t 300 K versus composition are measured. The temperature dependences of the total thermal conductivity and the thermoelectric figure of merit 2 are calculated. The composition with maximum value of 2 is determined as GeTe + 20 mol% AgSbTe,.The reasons for the maximum thermoelectric figure of merit for this composition and for the anomaly changes in the thermoelectric parameters and the sharp increase of 2 in the region of phase transitions (Oi-C&,)are discussed.Die thermoelektrischen Eigenschaften von polykristallinen Proben der Mischkristalle (GeTe)l -, * . (AgSbTe,), nahe der Verbindung GeTe mit den Zusammensetzungen z = 0,OO; 0,lO; 0,15; 0,20 und 0,29 werden untersucht. Die Temperaturabhangigkeiten der Thermospannung und des spezifischen elektrischen Widerstandes und die Abhiingigkeiten der thermischen Leitfiihigkeit bei 300 K von der Zusammensetzung werden gemessen. Die Temperaturabhingigkeiten der thermischen Leitfiihigkeit und des thermischen Wirkungsgrades 2 werden berechnet. Die Zusammensetzung mit dem Maximalwert von 2 wird bestimmt zu GeTe + 20 Molyo AgSbTe,. Die Ursachen fur den maximalen Wirkungsgrad bei dieser Zusammensetzung und fur das scharfe Anwachsen von 2 im Gebiet der Phesenumwandlung (Oi-Civ) fur alle Zusammensetzungen werden diskutiert.

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On the Fundamental Energy Gap in GeTe

Cited by 15 publications

References 6 publications

Electronic origin of the high thermoelectric performance of GeTe among the p-type group IV monotellurides

Electronic origin of the high thermoelectric performance of GeTe among the p-type group IV monotellurides

Effect of lithium doping on electrophysical and diffusion proper-ties of nonstoichiometric superionic copper selenide Cu1.75Se

Thermoelectric figure of merit of the system (GeTe)1−x(AgSbTe2)x

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