Query: structure of CdTe

Candidate papers:

abstract: Polarization of CdTe radiation detectors in the dark was studied theoretically by taking into account a wide set of detector characteristics relevant to the polarization. Drift diffusion and Poisson's equations were solved numerically in one dimension in time resolved regime, where the characteristic time is determined by the charging of detector bulk. Shockley Read Hall model describes the trapping/detrapping of free carriers. Both diode like (In,Al)/CdTe/Pt and symmetrical (In,Al,Pt)/CdTe/(In,Al,Pt) detectors were considered. We showed how the space charge is formed in time after detector biasing and a `dead layer' appears in the detector when the accumulated charge screens the bias. Numerical results were compared with the Conventional model of charge accumulation. The influence of temperature on polarization was analyzed and the polarization is correlated with current transient. The approach can be conveniently used to find principal properties of trap levels and contacts in semiconductor radiation detectors.
author_names: Roman Grill

Eduard Belas

Jan Franc

Marek Bugar

Stepan Uxa

Pavel Moravec

Pavel Hoschl
title: Polarization Study of Defect Structure of CdTe Radiation Detectors
venue: IEEE Transactions on Nuclear Science
year: 2011

abstract: Evidence concerning the defect structure of CdTe is reviewed with particular reference to the conditions producing high resistivity material.
author_names: F A Kroger
title: The defect structure of CdTe
year: 1977

abstract: Abstract A high temperature Hall effect study as function of cadmium pressure and temperature was carried out for pure and indium doped CdTe. The results, combined with published data on the Hall effect of quenched crystals and electronic energy level positions, are interpreted on the basis of a detailed point defect model. Parameters of the equilibrium constants of various defect formation reactions are given.
author_names: S S Chern

Honnavalli R Vydyanath

F A Kro"ger
title: The defect structure of CdTe: Hall data
year: 1975

abstract: Abstract In this work we report the influence of post deposition heat treatments on the structure of the CdTe films electro deposited on stainless steel substrates. The CdTe films were annealed in air at various temperatures and time in order to investigate the influence of post deposition heat treatments on the film structure. The various structural parameters, such as grain size, lattice constant and stress, were investigated using XRD. The results showed that the stress, grain growth and the re crystallization of CdTe depends on the post deposition annealing time and temperatures. In the initial stages of annealing when the grains grow in size, the grain growth process obeys a parabolic growth law. The re crystallization process during annealing has two stages, in the beginning, the re crystallization is dominated by random orientation of the grains followed by a second process in which once again the crystallites tend to orient in a particular direction. The value of activation energy for 20% re crystallization in CdTe was estimated as 1.17+ 0.1 eV. The as deposited film is under compressive stress and with annealing the compressive stress increases. For longer annealing times the stress changes from compressive to tensile. The calculated stress is ~10 9 dyn/cm 2 Lattice parameter of the as deposited film is larger than the powder sample and upon annealing lattice value increase and reaches a maximum and on further annealing for a long time it decreases and attains a value less than that of the powder sample. The calculated value of the change in band gap due to the stress, induced during the annealing, is in the range 13 meVD E g 17 meV.
author_names: Joel Pantoja Enriquez

Xavier Mathew
title: The effect of annealing on the structure of CdTe films electro deposited on metallic substrates
year: 2003

abstract: Single crystal CdTe specimens were deformed in compression at 25deg, 200deg, 300deg, and 500degC to various levels of plastic strain and to failure. Deformation characteristics at each temperature are given as curves of shear stress vs shear strain and the effect of test temperature on deformation behavior is examined. The dislocation structure of the CdTe samples deformed at high temperatures is examined using transmission electron microscopy. The relation between the deformation properties and the corresponding microstructure in CdTe is explored using previously developed models to describe metallic and nonmetallic crystalline materials.
author_names: Edward L Hall

John B Vander Sande
title: Plastic Deformation Behavior and Dislocation Structure of CdTe Single Crystals
year: 1978

abstract: Single domain CdTe(111)B has been grown on Si(001) substrates tilted 1o 2o, and 4o toward [110] All the layers started with a double domain structure, then a transition from a double to a single domain was observed by reflection high energy electron diffraction. A microscopic picture of this transition is presented. We also measured the tilt between CdTe(111)B and Si(001) The result does not follow the tilt predicted by the currently existing model. A new model of the microscopic mechanism of CdTe(111)B growth is presented. New evidence indicates that optimizing the tilt of the substrate surface is very crucial in improving the CdTe(111)B crystal quality.
author_names: Yong P Chen

Sivalingam Sivananthan

J -P Faurie
title: Structure of CdTe(111)B grown by MBE on misoriented Si(001)
year: 1993

abstract: The grain structure of CSS deposited CdTe/CdS solar cells was studied as a function of annealing time in the presence of CdCl 2 The structure was studied by chemically bevelling the cell to reveal the grains at all depths of the layer. The grain boundaries were revealed using a defect sensitive etch, and photomicrographs taken at intervals down the bevel. These photomicrographs were then analysed computationally. Histograms of grain radius for each micrograph were fitted well by the Rayleigh distribution. The average grain radii were found to vary linearly throughout the CdTe layer as r (0.107 x d) 1.06, where d is the distance from the interface. This behaviour was unaffected by the CdCl 2 treatment and is discussed with reference to a kinetic model of grain growth. Finally the use of correlation plots in analysing grain centroid distribution is described and some results presented.
author_names: M A Cousins

Ken Durose
title: Grain structure of CdTe in CSS deposited CdTe/CdS solar cells
year: 2000

abstract: The structure of CdTe/ZnTe superlattices has been analyzed through th/2th x ray diffraction, photoluminescence, and in situ reflection high energy electron diffraction (RHEED) measurements. Samples are found to break away from Cd_(x)Zn_(1 x)Te buffer layers as a consequence of the 6% lattice mismatch in this system. However, defect densities in these superlattices are seen to drop dramatically away from the buffer layer interface, accounting for the intense photoluminescence and high average strain fields seen in each of our samples. Observed variations in residual strains suggest that growth conditions play a role in forming misfit defects. This could explain discrepancies with calculated values of critical thickness based on models which neglect growth conditions. Photoluminescence spectra reveal that layer to layer growth proceeded with single monolayer uniformity, suggesting highly reproducible growth. Our results give hope for relatively defect free Cd_(x)Zn_(1 x)Te/Cd_(y)Zn_(1 y)Te superlattices with the potential for applications to optoelectronics offered by intense visible light emitters.
author_names: Richard H Miles

T C Mcgill

Sivalingam Sivananthan

Xiang-yong Chu

J -P Faurie
title: Structure of CdTe/ZnTe superlattices
year: 1987

abstract: The effect of ion milling on the defect structure of CdTe crystals has been investigated in the scanning electron microscope by cathodoluminescence. Enhancement in the luminescence intensity is observed after ion treatment. Luminescence spectra of treated and untreated zones of the samples indicate that ion milling causes generation of tellurium vacancies and filling of cadmium vacancies in a subsurface layer. In addition, enhancement of the concentration of cadmium vacancy related defects in the region extending up to from the layer is revealed. This effect is discussed in connection with models of p to n type conversion of CdTe during ion milling.
author_names: Gennady N Panin

Paloma Fernandez

Javier Piqueras
title: Effect of ion beam milling on the defect structure of CdTe
year: 1996

abstract: Atomic layer epitaxy (ALE) for growing II VI compound single crystal films has been described. The growth of CdTe films on p type CdTe(110) and (111)A substrates by ALE is shown to lead to high structural perfection. Surface crystal structure of these films is studied by LEED. The nonpolar (110) surface exhibits (1x1) symmetry while the polar (111)A surface is reconstructed showing (2x2) symmetry. Electronic valence band features are studied by angle resolved photoemission and preliminary analysis of the photoemission spectra is presented. Most of the features may be accounted for in terms of the bulk electronic structure via direct transitions including primary and secondary cone emission. An intrinsic surface state (surface resonance) likely associated with a Te derived dangling bond in the (110) film is observed.
author_names: M Pessa

O Jylha

P A Huttunen

Marian A Herman
title: Epitaxial growth and electronic structure of CdTe films
year: 1984