Surface-barrier structures on single crystals of CdMgMnTe quaternary solid solutions: Creation and properties (original) (raw)
Related papers
Production of structurally perfect single crystals of CdTe and CdZnTe
The European Physical Journal Applied Physics, 2004
Single-crystal ingots of CdTe and Cd0,96Zn0.04Te 60-100 mm in diameter were grown by directional solidification using the self-seeding technique. The microstructure of the crystals was checked by optical microscopy, electron microscopy (TEM, SEM and EBIC), cathodoluminescence, and X-ray diffraction. It was found that crystal perfection depends to a large measure on the temperature schedule during Lpostgrowth crystal cooling: special caution should be exercised in the temperature interval including the polymorphous transformation. A direct relationship between optical and electronic properties on the one hand and crystal microstructure on the other hand was established.
Investigations of Cd1−xMnxTe crystals by means of ellipsometry and Auger electron spectroscopy
Applied Surface Science, 2003
Cd 1Àx Mn x Te crystals, obtained by the high-pressure Bridgman method for x ¼ 0, 0.27, 0.49, 0.67 and 0.8, were investigated. Crystal composition was determined by electron microprobe analysis. For an Mn content lower than 0.7, a single phase of pure zinc blend structure was found. In Cd 0.2 Mn 0.8 Te samples a two-phase structure was revealed. Auger electron spectroscopy (AES) was used to determine the composition of the crystal surfaces. AES depth profiles obtained by argon sputtering and AES analysis allowed to find the distribution of Cd, Mn and Te inside the sub-surface region. Spectroscopic ellipsometry was applied to determine the complex dielectric function e of the samples. Ellipsometric measurements were performed at room temperature in the photon energy range 0.75-6.5 eV. The spectral dependence of e was used to find the energy gaps E g of the alloys with different Mn content. Ellipsometric data were correlated with the compositional results obtained from the electron microprobe and AES depth profile investigations. A linear increase of energy gaps with increasing x was observed for chemically homogeneous CdMnTe crystals. #
Is the (Cd,Mn)Te crystal a prospective material for X-ray and ?-ray detectors?
physica status solidi (c), 2005
To answer the title question-the technology and properties of the (Cd,Mn)Te crystals is discussed as compared with those of the more commonly used (Cd,Zn)Te crystals. The composition homogeneity of the large single crystals of the ternary compound seems to be easier to achieve in the case of (Cd,Mn)Te because the segregation coefficient of Mn in CdTe is negligible with respect to that (approx. 1.3) of Zn. Only 15% of MnTe has to be added to CdTe to reach the best for the detector application value of the energy gap (in the range 1.7-2.2 eV), while the necessary amount of ZnTe is over 30%! This is because the composition dependence of the CdTe energy gap is for Mn twice as strong as for Zn. Using a smaller amount of the second cation diminishes many alloying-related problems. Dopant-free as grown (Cd,Mn)Te crystals are of p-type, which is related to the Cd vacancies acting as acceptors. The number of vacancies can be reduced by the post-growth annealing in the Cd vapours and the high (~ 10 10 Ωcm) resistivity, required for good detectors, can be obtained by doping with donors. The technology of the (Cd,Mn)Te crystals, undoped and compensated in the very large range of concentrations, and Cdannealing of the samples is discussed. Characterization of the obtained crystals is described. The behaviour of the preliminary detectors is shown.
Growth and Characterization of (Cd, Mn)Te
IEEE Transactions on Nuclear Science, 2000
The present article presents technology, required for repeatable manufacturing of the 1.5 and 2 inch crystal rods of (Cd, Mn)Te is discussed. In order to obtain semiinsultaing crystals, compensation and annealing in Cd-vapours was used. Vanadium was mainly used as the compensating dopant. The resistivity of the obtained monocrystalline plates was around cm, and the -product was about cm /V. Mapping of the resistivity was performed on both as-grown crystals and the crystals annealed in the saturated Cd vapour. As-grown (undoped) crystals were inhomogeneous and their resistivities were in the range cm. After annealing resistivity increased up to -cm and better homogeneity could be seen. Annealing in saturated Cd-vapours had influence on tellurium inclusions/precipitates. It was studied by IR transmission microscopy. For as-grown samples the density of Te inclusions ( m) was cm but for annealed samples was cm . The concentrations (measured by SIMS) of the unintentional impurities Na, Ca, and Ga were in the region cm , corresponding well with the purity (6N) of the elements used for crystallization of our (Cd, Mn)Te. The low temperature photoluminescence (PL) measurements indicated significantly lowered concentrations of acceptors after annealing. Nearly ohmic contacts to the high resistivity (Cd, Mn)Te plates were obtained by deposition of the amorphous layers of heavily doped semiconductor (ZnTe:Sb). We undertook the present work to show that low vanadium doping level and proper annealing conditions are sufficient to obtain detector grade material.
Optical-Properties of MG-Based II-VI Ternaries and Quaternaries - CD1-XMGXTE and CD1-X-YMGXMNYTE
Physical Review B, 1993
We have investigated the photoluminescence, Raman, and infrared spectra of Cd~Mg Te and Cdi~" Mg Mn"Te bulk crystals with the zinc-blende structure. From the band-gap (Es) photoluminescence peak we deduce Eg= 1.595+ 1.607x + 1.592y eV at 10 K. The Raman spectra of the quaternary alloys exhibit a classic three-mode behavior with MgTe-like, MnTe-like, and CdTe-like LO-TO pairs of zone-center optical phonons, in decreasing order of frequency. Their composition dependence follows the modified random-element isodisplacement model. For very small x and/or y, the infrared absorption spectra recorded with a Fourier-transform spectrometer clearly reveal the local modes of Mn + and Mg +. Mn + exhibits one and Mg + three local modes corresponding to their isotopic abundances; the latter have frequencies proportional to 1/QMM 2+.
Crystal growth of CdTe alloyed with Zn, Se and S
Materials Science and Engineering: B, 1997
Single crystals of CdTe-based quaternary alloys are grown by a vertical Bridgman method. The lattice constant of the quatemary ingot is proposed to match that of Cd
2019
The structural, electronic and magnetic properties of Cd1-xMnxTe alloy in the zinc-blende (ZB) phase within the framework of spin-polarized density functional theory using the generalized gradient approximation (GGA) are studied. In particular, we employ GGA+USIC method that gives a better description of systems with strong Coulomb correlations of the d-electrons. First, we discuss implementation of GGA+U method to the ground state calculations of pure CdTe and ferromagnetic MnTe. The alloy is modelled at some selected compositions by ordered structures described in terms of periodically repeated supercells for the compositions x = 0.25, 0.5, and 0.75. The compositional dependence of the lattice constant, electronic band structure and partial densities of states of ferromagnetic Cd1-xMnxTe alloy are studied. We estimate the spin-exchange splitting energies produced by the Mn 3d-states and determine the exchange constants for the conduction and valence bands of the alloy. The energy ...
Growth and characterization of detector-grade CdMnTe by the vertical Bridgman technique
AIP Advances, 2018
We grew Cd1-xMnxTe crystals with a nominal Mn concentration of 5% by the vertical Bridgman growth technique. The compositional variation along the length of the grown ingot was studied by powder X-ray diffraction. The composition was found to be uniform along the growth direction. The achieved resistivity was 1-2.5 x1010 ohm-cm with a mobility-lifetime (μτ) product value for electrons of ∼1.7x10-3 cm2/V. An energy resolution of ∼7.5% at 662 keV was achieved for a 9-mm long Frisch grid detector fabricated from an ingot grown using as-received starting materials.