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Our research is motivated in the first line by the necessity to have the total control of the vacancies which appear during the growth of mercury telluride crystals. As it is known, this material is very important for the IR devices. We present a non-destructive method for quantitative determining the vacancy concentration in the lattice of Hg-based semiconductor alloys with tetrahedral structure. The method is based on the identification of additional vibrational modes (AVM) induced by lattice deformations in the far infrared (FIR) reflectivity spectrum. Although the method is restricted by sensitivity limitations, recent FIR experimental data carried out on HgZnTe and HgCdTe samples containing Hg-vacancies confirmed the presence of AVMs induced by Hg-vacancies in as-grown crystals. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Experimental results related to the growth by solid state recrystallization of different semiconductors such as HgCdTe, HgMnTe, CdTe, ZnSe and ZnS are reported and reviewed. The importance of the initial texture and of the deviation from stoichiometry is stressed and the essential role of metal vacancies is emphasized.

Experimental studies are conducted to investigate the influence of dislocations on the electrical and optical properties of CdTe crystals. The microindentation technique is performed at room temperature to generate dislocations on the Cd(1 1 1) and Te( 1 1 1 ) faces of nonintentionally doped n-type CdTe crystals. The effect of the generated dislocations is characterised by means of C – V measurements and photoluminescence experiments. The analysis of the results obtained confirms both the reduction of the donor concentration, essentially due to Cd vacancies, and the increase in the band-gap width. In addition, this analysis confirms the fact that the long arms of the indentation rosette consist of Cd(g)-type dislocations on the Cd face and Te(g)-type dislocations on the Te face. Finally, this study allows to specify the kind of majority defect on each face, V Cd on Te face and V Te on Cd face.

The interaction of vacancies with 111In atoms is studied in Hg1−xCdxTe compounds via perturbed-angular correlation (PAC) experiments, for x=0.065, 0.21, 0.44, and 0.95. In the low-x (Hg-rich) compounds, Hg vacancies are created by heating in vacuum. For the x=0.21 alloy, we have previously shown that InC-vacC pairs (A centers consisting of an In atom on a cation site and a vacancy at a neighboring cation site) are abundant after quenching from elevated temperatures. These defects are characterized by two PAC signals with quadrupole interaction frequencies νQ1=83 MHz and νQ2=92 MHz, and asymmetry parameters η1=η2=0.08. For the x=0.065–0.44 alloys, the data presented in this article show that the fractions f1 and f2 of In atoms associated with these two frequencies vary with x according to whether one or two Hg atoms are nearest neighbors to the Te atom that is bound to the In atom and the vacancy. The data are explained by the polarizable point-ion model. For the x=0.95 compound, PAC signals are observed o...

High-resistivity vanadium-doped CdTe and CdZnTe crystals were investigated by photoluminescence in the near-infrared spectral range. The observed shift of the near band edge luminescence with respect to the sample position along the ingot is explained in terms of a non-uniform distribution of zinc. Two deep luminescence bands were detected at around 0.8 eV and 1 eV. The electron - phonon interaction strengths (Huang - Rhys parameter S) of the two related centres have been estimated and a configuration coordinate diagrams proposed. The 0.8 eV emission band is assigned to the electrically active eV centre. The double peaked shape of the 0.8 eV emission band is a result of either an overlap between two emissions bands or the Jahn - Teller effect including a small quadratic effect. In the framework of the first hypothesis, the emission band is interpreted as a combination of two simultaneous recombination processes: the internal transition and the conduction band level transition.

Le semi-conducteur II-VI, ZnSe, dope au Cr 2+ presente une emission laser dans le moyen infrarouge entre 2 et 3μm a 300K. Une accordabilite en longueur d'onde entre 2.2 et 2.62μm a deja ete observee. L'interet des polycristaux de ZnSe en tant que materiau hote pour le Cr 2+ est non negligeable en terme de cout et de dimension comparativement aux monocristaux. L'etude des deux types de matrice a permis de quantifier les pertes et les efficacites laser. En regime de commutation de gain, le polycristal presente une efficacite optique-optique de 28% contre 33% pour un monocristal de Cr 2+ : ZnSe.

Similar ternary semiconductors are sometimes associated with widely different structures characterized by different site occupation preferences. We have used far-infrared (FIR) spectra to determine the site occupation preference coefficients for three ternary semiconductor alloys: ZnCdTe, ZnHgTe and CdHgTe and, in the case of ZnHgTe, have validated it by X-ray absorption fine structure (EXAFS) analysis. While ZnCdTe spectra exhibit the canonical configuration with eight phonon lines free of vibrational defect lines and only a slight departure from a random ion distribution, CdHgTe spectra show the eight canonical phonon modes plus an additional vibrational defect line and constant preference coefficients. In contrast, two defect lines and only four modes characterize ZnHgTe spectra, as extreme preferences prevent the formation of two of the five expected tetrahedral configuration arrangements. Moreover, for this system, comparison with EXAFS data points out the vibrational nature of both the extra lines. The analysis clearly shows that assuming a Bernoulli distribution of the component configurations of semiconductors may lead to wrong assessments of the evolution of its properties with relative content., JRC.D.5-Standards for Food Bioscience

The buildup of damage caused by In ion implantation (320 keV, 1012–1015 cm−2) in Hg1−xCdxTe (x=0.24) (MCT) and Hg1−xZnxTe (x=0.16) (MZT) is studied by means of Rutherford backscattering spectroscopy (RBS) channeling along the

The local structure of ZnTe has been studied up to 30 GPa by x-ray absorption spectroscopy at the Zn K-edge. Phase transitions were observed at 9.5±0.5 and 12.±0.5 GPa. From the EXAFS and XANES studies it is deduced that ZnTe-II has as tetrahedral structure and ZnTe-III a distorted octahedral. A first order Mumaghan equation of state has been fitted to the first neighbors distances in phase I, giving a bulk modulus of 56 GPa.

1S and 2P excitons in ZnTe are studied by two-photon absorption with uniaxial stress up to 350 MPa. The energy shift and splitting which is caused by the stress-induced valence band splitting and the envelope-hole coupling allows the determination of deformation potentials.

The main characteristics of ZnSe as material for substrates are compared with those of other classical substrates such as InP, GaAs, Si or (Cd,Zn)Te. The role of ZnSe substrates for the growth of epitaxial ZnSe layers is discussed. ZnSe bulk crystal growth is reviewed and the reasons for the poor crystalline quality of ZnSe are analysed. This has led to some suggested approaches to the growth of twin-free ZnSe crystals either by doping or by low-temperature growth. Finally the future of ZnSe as a substrate is considered.

We present a nondestructive method for quantitative determination of the vacancy concentration in the lattice of Hg-based semiconductor alloys with tetrahedral structure. The method is based on the identification of additional vibrational modes (AVMs) induced by lattice deformations in the far-infrared (FIR) reflectivity spectrum. Although the method is restricted by sensitivity limitations, recent FIR experimental data carried out on HgZnTe and HgCdTe samples containing Hg vacancies confirmed the presence of AVMs induced by Hg vacancies in as-grown crystals.

The extremely high susceptibility of MCT to any external action is reviewed. The stability concept is analysed through two different approaches, at the microscopic and the macroscopic scales. The choice among numerous potential candidates to IR detection can be helped by some selection criteria; these include stability, which can be estimated through microhardness measurements, or ordering, which refers to the electronic properties. The II-VI mercury-based ternary alloys can be compared with other candidates such as pyroelectric detectors, silicon and low-dimensional solids, mainly III-V superlattices. Some futuristic materials or exotic structures are proposed through the application of band-gap engineering and structural engineering concepts.

The authors have performed transport experiments under hydrostatic pressure on samples of two different narrow-gap mercury telluride mixed compounds: Hg1-xCdxTe (x=0.27, 0.28, 0.30) and Hg1-xZnxTe (x=0.15). The investigated samples of HgCdTe are n-type samples grown by the molecular beam epitaxy technique on GaAs/CdTe substrates and doped with In during the growth. The experiments, performed at liquid helium temperature in the magnetic field range B=0-5 T and under hydrostatic pressure up to P=11 kbar, allow them to conclude that this doping process does not induce any resonant impurity level as previously observed for boron-implanted samples. They used the same experimental techniques (0

Summary form only given. We present what we believe to be the first largely tunable (8-12 /spl mu/m) difference frequency generation (DFG) obtained in GaAs and ZnSe plates, using quasi-phase matching by total internal reflection QPM-TIR in one single slab.

The photorefractive effect is now extensively studied in semiconductors, in particular for applications to optical communications.

Ternary AII XBVI, and to a very little extent, quaternary A 1 II A 2 II XBVI alloys, with X being essentially Mn, and with a small insight to other transition metals and some rare earths, will be considered in this review. These alloys have drawn considerable attention during the past decade because of their magnetic properties which will be emphasized in other courses.

Electrical measurements and photoluminescence experiments were performed on several CdTe and Cd 0,96 Zn 0,04 Te crystals with dislocation density in the range 5x10 4 -6x10 5 cm - 2. The observed variation in electron mobility has been interpreted in terms of scattering on space charge regions surrounding dislocations, a related reduction in the effective volume of the crystals, and excess scattering due to a non ideal alloy behaviour. The linewidth of the acceptor-bound exciton recombination line includes contributions due to alloy disorder and dislocations, the latter being enhanced in the alloys Des mesures electriques et des experiences de photoluminescence ont ete realisees sur des cristaux de CdTe et de Cd 0,96 Zn 0,04 Te, de densite de dislocations variant entre 5x10 4 et 6x10 5 cm -2 . La variation de la mobilite electronique a ete interpretee en termes de: diffusion sur les regions de charge d'espace entourant les dislocations, reduction correspondante du volume effectif des cristaux, diffusion en exces dans les alliages due a leur caractere non ideal

The escape rate of fluorescent radiation as a function of active region thickness is calculated for CdTe detectors. A detailed analysis of the theoretical model is given. A convenient method of estimating the active layer thickness from the gamma-ray spectrum is presented. The theoretical predictions are compared with experimental results obtained with n-type CdTe detectors.

Highly perfect n-type CdTe single crystals grown by the sealed-ingot-zone refining method have been used to fabricate semiconductor surface-barrier detectors for X- and low-energ, γ-ray analysis. An energy resolution of 2.0 keV /fwhm/ and 1.5 keV /fwhm/ was achieved for 59.5 keV γ-rays from 241Am and 5.9 keV characteristic K X-ray line from 55Fe source, respectively. Spectra were measured at room temperature with low detector bias. The observed full energy peak of 59.5 keV γ-rays has been compared with the teoretical peak calculated for a surface-barrier junction with fixed space charge, the trapping effects being taken into account.

Cadmium telluride detectors were fabricated from low resistivity (50–500 Ω·cm) n-type crystals grown by the sealed-ingot-zone refining method. Physical parameters of this kind of detector were discussed and the factors influencing them were analysed. The main advantage of n-type low resistivity CdTe detectors is high energy resolution for low energy X- and γ-rays at room temperature; the best value for the 5.9 keV line from a 55Fe source was 1.1 keV fwhm. The main limitation is small active volume (diameter of active surface 1–2 mm, thickness of active region below 100 μm), which is relevant to the counting efficiency and the range of registered γ-energies. As a result of the performed analysis a miniature room temperature probe with high energy and spatial resolutions was designed.

The interaction of electrons and polar-optical phonons is investigated for CdTe and InP in cylotron resonance (CR) emission and absorption experiments. Under hot electron conditions three different Landau level transitions are observed. From the positions of the fundamental transition and the CR line splittings the nonparabolicity and the polaron contribution to the effective mass are analysed using a variational approach for the polaron shifts. The bare band edge masses and the polaron coupling constants are determined to be m ∗ 0 = 0.0900±0.0005 , α=0.35+-0.03 for CdTe and m ∗ 0 = 0.0765±0.0005 , α=0.15±0.01 for InP.

The different techniques of making ohmic contacts to p-type CdTe are reviewed and discussed. Mercury telluride, whose work-function matches perfectly that of p-type CdTe, is shown to be more favourable than Au or Pt. The HgTe contacts deposited by close spacing isothermal growth present a room temperature specific contact resistance ten times lower than so far reported. Hall effect measurements have been performed down to low temperatures on several undoped p-type CdTe and Cd0.7Hg0.3Te crystals. Ionisation energies of 0.05-0.07 and 0.13 eV for CdTe and 0.024 eV for Cd0.7Hg0.3Te have been determined and the nature of the responsible centres discussed.

The buildup of damage induced by In ion implantation into Hg1−x Cdx Te for various composition (x=0, x=0.24, x=0.4, x=0.7, and x=1) was measured by means of channeling Rutherford backscattering spectroscopy (RBS). Damage profiles were extracted from the spectra using a model based on Quere’s dechanneling treatment. Despite the large difference in bond nature and the related physical properties between the different compositions, the general trends in damage formation were found similar for all x values studied, though displaced by about two orders of magnitude in dose, HgTe damaging much easier than CdTe. For all compositions, different types of damage seem to be created at different stages during the implantation. The results can be understood if agglomeration of point defects to extended defects followed by a redistribution of the defects to deeper lying clusters with increasing dose is assumed.

En étudiant le CdTe dopé au chlore par des techniques de mesure de capacité de jonction, nous avons découvert un nouvel aspect des effets anormaux associés à l'incorporation du chlore dans CdTe ainsi que cela avait été déjà publié. Nous avons mis en évidence l'existence d'un piège à électrons, mais il y a une différence importante entre les résultats de mesures de capacité thermostimulée (ΔE = 0,41 eV) et de photocapacitance (piège situé à peu près au milieu de la bande interdite). Les mêmes résultats ont été obtenus sur des échantillons contenant la même quantité de chlore mais différent par le taux d'auto-compensation. Les différents modèles utilisés jusqu'à présent pour expliquer le comportement de CdTe dopé au chlore sont exposés : modèle de centre double accepteur et modèle de donneur non-Γ. Nous avons été amenés à repousser ces modèles et à proposer un modèle non purement électronique : deux atomes de chlore sont impliqués dans chaque centre, un des deux atomes pouvant occuper deux sites dans le réseau. A chaque configuration correspond un état de charge donné du centre et une énergie d'ionisation électronique différente. Les expériences de thermostimulation sont celles qui sont associées au changement de configuration microscopique du centre qui entraîne le dépiégeage des électrons.

The magnetic susceptibility of Zn1−xMnxSe (0.02 ≤ × ≤ 0.53) and Zn1−xMnxTe (0.07 ≤ × ≤ 0.21) was investigated in the temperature range 10 mK

Localized defects are investigated in p-CdTe:Cu doped by copper incorporation during Bridgman growth. The results of Hall measurements, admittance spectroscopy and photoluminescence (PL) are similar to those obtained from samples Cu-doped by ion-implantation or diffusion : copper is incorporated as a substitutionnal acceptor in Cd site with an activation energy 0.15 eV. The as-grown character of the Cu-doped samples, without any annealing treatment, rules out any correlation between the 1.5896 eV PL line and annealing processes and attributes definitively this line to excitons bound to Cu Cd acceptors. Copper can be detected without any ambiguity in further technologic applications of CdTe to optoelectronic device purpose.

Low-resistivity (102–104 Ω cm) n-type CdTe surface-barrier detectors have been produced and measured. The energy resolution at 300 K was found to be 32 keV (fwhm) for 6.050 MeV α-particles and 14 keV (fwhm) for 59.5 keV γ-rays. The average energy required to produce the free electron-hole pair in n-type CdTe single crystals at 300 K for α-particles was determined experimentally, and a value of ϵCdTe,α = (4.43±0.03) eV was obtained.

Photothermal deflection spectroscopy (PDS) was used to analyze CdTe thin films which are to be used to construct solar cells. It was found that CdTe thin films grown on a conducting SnO 2 layer deposited on glass show deviations from a stoichiometric composition due to an excess of tellurium. This non-stoichiometry modifies the absorption spectrum obtained from the PDS measurements.

From the preceding experimental study on the thermoelectric properties of Bi2Te3, a mixedscattering model was used to fit the sharp variations of the various parameters with stoichiometric deviations. First a one-band model was developed: the Fermi level and the main scattering mechanism were determined and values for the Hall factor, the Lorenz number, the effective mass and the relaxation time constant found for both n- and p-type material. Using a two-band model permitted the fitting of the behaviour of the thermoelectric parameters in the vicinity of the change in type. The optimum Fermi level for the maximum of the figure of merit was found just at the bottom of the conduction band.

La luminescence, la reflectivite et la diffusion de Raman resonnante par des phonons LO du Cd 1−x Zn x Te (x∼0,5) non dope, ont ete etudiees dans la gamme spectrale proche de la bande interdite a basses temperatures. On identifie l'intervalle des excitons 15 intrinseques a l'aide du spectre de reflectivite et de la decomposition de Zeeman de la luminescence excitee selectivement. Presentation d'un modele qui suppose que le profil de la diffusion de Raman resonnante par des phonons determines par la diffusion des excitons 15 etendus par les fluctuations aleatoires du potentiel