Anomalously small resistivity and thermopower of strongly compensated semiconductors and topological insulators

Tianran Chen, B. I. Shklovskii

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Abstract

In the recent paper, we explained why the maximum bulk resistivity of topological insulators (TIs) such as Bi2Se3 is so small. Using the model of completely compensated semiconductor we showed that when the Fermi level is pinned in the middle of the gap the activation energy of resistivity is Δ=0.3(Eg/2), where Eg is the semiconductor gap. In this paper, we consider a strongly compensated n-type semiconductor. We find the position of the Fermi level μ calculated from the bottom of the conduction band Ec and the activation energy of resistivity Δ as a function of compensation K, and show that Δ=0.3(Ec-μ) holds at any 0<1-Kâ‰1. In the same range of relatively high temperatures, the Peltier energy (heat) Π is even smaller: Πâ‰Δ/2=0.15(Ec-μ). We also show that at low temperatures, the activated conductivity crosses over to variable range hopping (VRH) and find the characteristic temperature of VRH, TES, as a function of K.

Original languageEnglish (US)
Article number165119
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume87
Issue number16
DOIs
StatePublished - Apr 15 2013

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