High-temperature injection spectroscopy of deep traps in CdTe polycrystalline films

The paper provides the direct experimental method to determine the localized state energy distribution function for semiconducting solid materials based on space-charge-limited current-voltage characteristics. The current-voltage characteristics would be obtained under the random temperatures. The Tikhonov regularization method was used to solve the Fredholm 1st rank equation. The method developed in this research was used for the study of deep traps in CdTe polycrystalline films obtained in quasi-closed-tube on the conducting substrate. In the bend gap of the material, some traps were traced, which can be described by the close to Gaussian distribution parameters as well as by the parameter of energy disorder = 0.015-0.04 eV. The research shows that the trap concentration and depend on the physical and technological conditions of the obtained films, while the energy of the traps depends on the impurity-defective material structure

Optical Losses of Thin Solar Cells on the Basis of n-ZnS / p-CdTe and n-CdS / p-CdTe Heterojunctions

The optical reflection and absorption losses in the accessory layers of solar cells based on n-ZnS / p- CdTe and n-CdS / p-CdTe heterojunctions are defined in this work. Aluminum doped zinc oxide is used as the front conductive layer material. It is shown that the replacement of traditional window material (CdS) for a wide-one (ZnS) leads to an increase in accessory solar cells layers transmittance. When the thickness of the window layers is 50 nm, the transmittance using ZnS windows with the wavelength of 380-500 nm is higher in 7-40 % than the corresponding value for CdS. At 300 nm for the same spectral field the difference increases to 8-89 %. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3559

Calculation of Fermi level location and point defect ensemble in CdTe single crystal and thin films

With the use of expressions obtained from the “first principles”, the ensemble of point defects was calculated, and the location of a Fermi level in undoped cadmium telluride single crystals and thin films depending on physico-technological conditions of their fabrication and annealing is determined. The model in use accounts the most complete spectrum of defects in chalcogenide, including defects in the cadmium and tellurium sublattices, and the existence of an antistructural defect on the cadmium sublattice. Calculations of the concentration of neutral and charged defects are realized for two extreme cases – full equilibrium and quenching. The comparison of the obtained results with the data of modeling provided with the use of a quasichemical formalism for a number of models most used presently is carried out. It is shown that all models describe well the results of Hall measurements of the concentration of free carriers in single crystals in the range of high cadmium pressure, but give essentially different results in the range of high tellurium pressure. Dominant defects in single crystals at high cadmium pressure and annealing temperatures are twice charged tellurium vacancies or interstitial cadmium atoms, which is in agreement with experimental results, as just such defects can provide the dependence of the concentration of free carriers on cadmium pressure as n ~ P¹/³Cd . A type of defects which are dominant in a tellurium-enriched material is determined by the chosen model. This allows us to make conclusions about the validity of the considered models and to specify the thermodynamic parameters of the defect creation processes in a material. The offered model can be used for modeling the ensemble of point defects in any А₂В₆ compounds. Thus, the problem of the choice of models adequate to experimental data is reduced to the determination of the creation energy for uncharged defects and the depth of energy levels of charged defects

Structural and optical characteristics of ZnSe and CdSe films condensed on non-oriented substrates

In this work, the complex investigation of structural and optical properties of zinc and cadmium selenide semiconductor films deposited by close-spaced vacuum sublimation method using thermal evaporation on non-oriented substrates was carried out. The structural and phase analyses of the layers condensed at different substrate temperatures were performed. The transmission and reflection spectra of the investigated films have been measured and their main optical characteristics have been calculated

Structural and electrical properties of ZnS/CdTe and ZnTe/CdTe heterostructures

We investigated the structural, substructural and electrical properties of ZnS/CdTe and ZnTe/CdTe heterostructures obtained by the close-spaced vacuum sublimation. It was found that the structural properties of CdTe and ZnTe thin films deposited on ZnS or CdTe sublayers are better than those of the films obtained on glass substrate at the same growth conditions. XRD-analysis has shown that Zn(x)Cd(1- x)Te(x = 0.21-0.30) solid solutions having the cubic phase were formed near the films’ interfaces. Furthermore, the saturation current, the ideality factor and the value of the potential barrier height were determined by the analysis of dark currentevoltage characteristics. This makes it possible to establish optimal growth conditions of ZnS/CdTe heterojunctions. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3016

Influence of solution precursors on structure of ZnO films

In the work using high resolution scanning electron microscopy and X-ray analysis, we carry out the studying of the correlation between chemical and technological conditions of deposition, the initial solution composition and structural properties of the synthesized samples of zinc oxide. Growth of the layers depends on the initial precursors and it occurs through formation of the ordered array of nanorods and nanoflowers. It is shown that it is possible to choose the optimal conditions to obtain ZnO films with controlled structural properties that can be used as the base layers in microelectronic devices

Ensemble of point defects in CdTe single crystals and films in the case of full equilibrium and quenching

The ensemble of point defects in CdTе undoped single crystals has been modeled. Two extreme cases were calculated: full equilibrium and quenching. Dependences of the point defect and free carrier concentrations on technological parameters of growing, post-growth annealing in Cd vapor, and the sample examination temperature have been studied. The growth conditions of single crystals and n- and p-type conductivity CdTе films were defined. The results obtained have been compared with experimental data. This made it possible to make conclusions concerning validity of the studied models and to propose additional experiments to make final choice between them.Проведено моделирование ансамбля точечных дефектов в нелегированных монокристаллах и пленках теллурида кадмия. Расчеты выполнены для двух крайних случаев - полного равновесия и закалки дефектов. Получены зависимости концентрации собственных дефектов, свободных носителей заряда от технологических параметров выращивания, послеростового отжига в парах кадмия и температуры исследования образцов. Определены условия изготовления монокристаллов и пленок CdTе n- и p-типа проводимости. Проведено сравнение полученных результатов с экспериментальными данными, что позволило сделать выводы относительно обоснованности рассмотренных моделей и предложить дополнительные эксперименты, позволяющие сделать окончательный выбор между ними.Проведено моделювання ансамблю точкових дефектiв у нелегованих монокристалах i плiвках телуриду кадмiю. Розрахунки виконано для двох крайнiх випадкiв - повної рiвноваги i загартування дефектiв. Одержано залежностi концентрацiї власних дефектiв, вiльних носiїв заряду вiд технологiчних параметрiв вирощування, пiсляростового вiдпалу у парах кадмiю i температури дослiдження зразкiв. Визначено умови виготовлення монокристалiв i плiвок CdTе n i p-типу провiдностi. Проведено порiвняння отриманих результатiв з експериментальними даними, що дозволило зробити висновки щодо обгрунтованостi розглянутих моделей i запропонувати додатковi експерименти, якi дозволяють зробити остаточний вибiр мiж ними

Structural and microstructural properties of Cd₁-xZnxTe films deposited by close spaced vacuum sublimation

The structural properties (microstresses, texture, lattice parameter, coherent scattering domains size) and chemical composition of Cd₁₋xZnxTe (CZT) films with variable zinc concentration were studied. Films were deposited on molybdenum coated glass substrates by close spaced vacuum sublimation method. Properties of samples were investigated by X-ray diffraction, energy dispersive spectroscopy, scanning electron microscopy. Zinc concentration in CdZnTe layers was determined by the EDS and from the lattice parameter, according to the literature data. Namely, it was determined that the CZT films had following Zn concentrations: x = 0.09, x = 0.24, x = 0.30