Tm Doping of Lead Telluride
- PDF / 196,868 Bytes
- 4 Pages / 414.72 x 648 pts Page_size
- 46 Downloads / 199 Views
Tm DOPING OF LEAD TELLURIDE
LUDMILA 1.RYABOVA AND MARINA E. TAMM Moscow State University, 119899, Moscow, Russia
ABSTRACT Doping with the rare earth elements is widely used for the improvement of parameters of the PbTe-based lasers. It has been found that Tm is a donor in PbTe, and the solubility of TmTe in PbTe does not exceed 7 - 8 mol.%. Electron concentration in obtained PbTe(Tm) crystals reaches 4.1020 cm-3 and depends on Tm content and on deviation from stoichiometry. The analysis of the magnetoresistance oscillation picture shows no variation of the energy spectrum parameters for Tm contents less than I at.%. The g-factor does not change as well. This may be due to a rather small exchange interaction between Tm atom, which is magnetic in both +2 and +3 valence states, and band electrons. The experimental data for PbTe(Tm) are compared with the properties of semimagnetic PbTe(Cr) with quite the same electron consentration value. INTRODUCTION The rare earth metals (REM) are widely used as dopants for the modification of lead telluride properties. It is possible to attribute them to two groups. The first group includes all REM excepting Eu, Sm, Yb and Tm. The metals forming that group appear to be in 3' valence state in their monotellurides which are found to be metals. In lead telluride they act as donors. Being characterized by low diffusion coefficients these elements have some advantages for the creating of multilayers based on PbTe with minimal thikness of each transition layer. Four excepted elements may be included into the second group. Their monotellurides are semiconductors with 2+ valence state of the metals. It was expected that in PbTe they will be neutral impurities and their solid solutions with lead telluride will be characterized by variable energy gap [1-3]. This suggestion was proved for Eu and Sm. The investigation of Tm doped lead telluride has been performed to complete the information concerning REM as dopants. EXPERIMENTAL Tm solulibility in PbTe along the cross-section PbTe-TmTe and the melting temperature of the alloys in the composition range 0 - 13 morl% TmTe have been investigated. The mixture of lead telluride with Tm monotelluride was used as a growth melt. Synthesis of TmTe was performed using a three staged technology described in paper [4]. As grown TmTe has been a single phase crystal with a parameter of the cubic lattice a = (6.33 ± 0.03) A. PbTe single crystals used as a component of the growing melt were p-type with hole concentration p - 1.2 1018 cm- 3 . The alloyed polycrystalline Pbl-xTmxTe samples were annealed at T = 750 C during 120 hours. It has been determined with the help of X-ray diffraction analysis that the solubility of TmTe in PbTe does not exceed 7 - 8 mol%. PbTe(Tm) single crystals were grown by the directed crystallization (DC) of the melt and by the vapour-liquid-solid (VLS) mechanism. All of the samples were n-type. The electric Mat. Res. Soc. Symp. Proc. Vol. 301. @1993 Materials Research Society
226
parameters of the samples are represented in the
Data Loading...
