Chromium Impurity States in Pb 1-x Ge x Te Alloys Under Pressure
- PDF / 130,541 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 27 Downloads / 152 Views
0987-PP03-02
Chromium Impurity States in Pb1-xGexTe Alloys under Pressure Evgeny Skipetrov1, Alexey Plastun1, Boris Kovalev1, Lyudmila Skipetrova1, Tatyana Topchevskaya1, and Vasily Slyn'ko2 1 Faculty of Physics, M.V. Lomonosov Moscow State University, Leninskie Gory, 1, Moscow, 119992, Russian Federation 2 Institute of Material Science Problems, Chernovtsy, 274001, Ukraine
ABSTRACT The galvanomagnetic effects in the n-Pb1-xGexTe:Cr (x=0.02-0.13) alloys at the temperatures 4.2≤T≤300 K and under hydrostatic compression up to 17 kbar have been investigated. The metal-insulator transition under the increase of germanium content in the alloys and insulatormetal transition, induced by pressure in Pb1-xGexTe:Cr (x=0.10) alloy, were revealed. Using the experimental data in the frame of two-band Kane dispersion relation the dependences of the free electron concentration and the Fermi level position on the matrix composition and on the pressure were calculated. The composition and pressure coefficients of chromium deep level movement were obtained and the models of the electronic structure reconstruction under varying the alloy composition and under pressure were proposed. INTRODUCTION Doping with magnetic mixed-valence impurities (Eu, Gd, Yb, Ti, Cr …) induces an appearance of deep impurity states in the electronic structure of PbTe-based narrow-gap semiconductors and turns them into the diluted magnetic semiconductors [1, 2]. The specific feature of these materials is that the magnetic activity of impurity ions is directly connected with their charge activity [3-5]. For example, substituting the metal in the host semiconductor lattice, the Yb impurity atoms can contribute as either electrically neutral and non-magnetic Yb2+ (4f14) ions or electrically and magnetically active Yb3+ (4f13) ions. The concentration of non-magnetic ions are corresponded to the density of occupied with electrons states in ytterbium deep level and the concentration of magnetic ions – to the density of empty states in the impurity level. Under these conditions the magnetic properties of the PbTe-based alloys are determined not only by the concentration of impurity introduced but also by the occupancy of impurity deep levels and hence by the mutual arrangement of the deep impurity level, the allowed band edges and the Fermi level [4, 5]. In PbTe chromium impurity deep level ECr situates in the conduction band, stabilizing the Fermi level approximately on 100 meV higher than its bottom [6-8]. We suppose that similar to the situation with ytterbium impurity level in PbTe-based alloys the energy position of chromium deep level relative to the allowed band edges should be very sensitive to the alloy composition and hydrostatic compression. However, the electronic structure of PbTe-based alloys doped with chromium is not yet investigated. In the present work the galvanomagnetic properties of the n-Pb1-xGexTe:Cr alloys were studied under variation of matrix composition (0.02≤x≤0.13) and under hydrostatic compression
(P≤17 kbar). It was supposed that v
Data Loading...
