Effect of Pressure on Electronic Structure of Pb 1-x Sn x Te Alloys Doped with Gallium
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0929-II04-21
Effect of Pressure on Electronic Structure of Pb1-xSnxTe Alloys Doped with Gallium Evgeny Skipetrov1, Alexander Golubev2, Nikolay Dmitriev1, and Vasily Slyn'ko3 1 Faculty of Physics, M.V.Lomonosov Moscow State University, Moscow, 119992, Russian Federation 2 Faculty of Material Sciences, M.V.Lomonosov Moscow State University, Moscow, 119992, Russian Federation 3 Institute of Material Science Problems, Chernovtsy, 274001, Ukraine
ABSTRACT The galvanomagnetic effects in the n-Pb1-xSnxTe:Ga (x=0.09-0.21) alloys at the temperatures 4.2≤T≤300 K and under hydrostatic compression up to 16 kbar have been investigated. It is shown that in all samples and in the whole investigated pressure range temperature dependencies of resistivity and Hall coefficient have a “metallic” character, indicating stabilization of Fermi level by the impurity resonant level. Using the experimental data in the frame of two-band dispersion law the dependencies of the free electron concentration and the Fermi level position upon temperature, matrix composition and pressure were calculated. The temperature, composition and pressure coefficients of gallium resonant level movement were obtained and the electronic structure under varying the alloy composition and under pressure were built. INTRODUCTION Doping of lead telluride based alloys with mixed valence impurities (In, Ga, Tl, Cr, Gd, Yb, etc.) leads to appearance of deep impurity levels stabilizing the Fermi level in the gap or on the background of allowed bands [1, 2]. In PbTe among the dopants mentioned above gallium is the sole impurity that induces the deep level situated within the gap, slightly above the middle of the gap. Hence gallium doping makes it possible to realize a dielectric state with extremely low, close to intrinsic values of the free charge carrier concentration in the fairly narrow range of impurity concentration (CGa=0.2-0.7 mol. %). At the same time there are some experimental data indicating existence of the second gallium-induced defect level lying on the background of conduction band and stabilizing the Fermi level at higher gallium concentrations [3-7]. In particular, our recent studies of Pb1-xGexTe:Ga (0.04≤x≤0.08) shows that there are at least two different impurity levels EGa1 and EGa in the energy spectrum of charge carriers in these alloys [6, 7]. The second impurity level EGa also situates in the gap under the conduction band bottom L6– of investigated alloys. The energy position of this level depends on the germanium concentration by the linear law: EGa-L6– ≈ 45-1980x meV. So, we have supposed that in PbTe this level should be resonant level situated in the conduction band and lying approximately on 45 meV higher than its bottom. However, there are still no direct experimental evidences of the existence of this gallium resonant level in the conduction band of PbTe and PbTe-based alloys. This research was devoted to the investigation of the effect of alloy composition and hydrostatic compression on the galvanomagnetic properties of the Pb1-xSnxTe al
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