Oscillatory Behavior of Thermoelectric Properties in p-PbTe Quantum Wells

Abstract

The room-temperature dependences of the Seebeck coefficient, Hall coefficient, electrical conductivity, charge carrier mobility, and thermoelectric power factor were obtained as a function of thickness d (d = 8 nm to 400 nm) of PbTe epitaxial layers grown by thermal evaporation in vacuum of PbTe polycrystals doped with Na onto (100)KCl surfaces and covered with an Al 2 O 3 layer. Distinct oscillations in the d-dependences of the properties were observed and attributed to the size quantization of the energy spectra in PbTe layers. The experimental values of the oscillation period are in good agreement with the results of theoretical calculations using the effective-mass approximation and a model for a rectangular potential well with infinitely high walls. It follows from the obtained results that quantization of the energy spectrum in PbTe thin-film structures occurs not only for the electron gas but also for the hole gas.

Quantum size effects and transport phenomena in PbSe quantum wells and PbSe/EuS superlattices

“…In [2], we reported the observation of oscillations in the thickness dependences of the transport properties in PbSe quantum wells (QWs) and attributed them to the QSEs. Later we observed similar oscillations in other IV-VI QWs (see e.g., [3,4]). …”

Quantum Size Effects And Transport Phenomena In Semiconductor IV-VI—Based 2D-Structures

“…Thin films were covered with EuS or Al 2 O 3 layers which protected the IV-VI layers from oxidation and acted as barrier layers. The details of the determination of electrical conductivity σ, Hall coefficient R H , Seebeck coefficient S, charge carrier concentration n(p) and mobility μ H were described in [3][4][5][6][7][8][9][10].…”

“…2) The quantum oscillations of kinetic coefficients occur for both the electron gas (PbTe [4,6,9], PbSe [3,6], PbS [5] and the hole gas (SnTe [8], PbTe [10]). …”

“…For example, for n-PbTe films prepared from crystals with n≈1.5⋅10 18 cm -3 , 3.8⋅10 18 cm -3 , and 7⋅10 19 cm -3 , we obtained Δd ≈ 32.5, 20.0, and 15 nm, respectively. [10] manifest themselves even at room temperature. 5) When epitaxial films grow in the island fashion (in contrast to the layer-by-layer one), it complicates determination of Δd in case of small Δd values [7,8].…”

“…The observed effects were attributed to the manifestation of QSEs in the PbSe QWs. Later these studies were continued and the range of objects was expanded with a view to establishing the influence of various factors on the oscillatory phenomena [4][5][6][7][8][9][10].…”