Marian Kuzma

Anisotropically etched Si surface and the electrical properties of Si/HgCdTe heterostructures

Abstract We used (001)-oriented silicon wafers, chemically etched under special conditions, as substrates for laser epitaxy of HgCdTe. Three types of Si surface with different microrelief were obtained: flat, pyramid-like and plate-like. Thin films of HgCdTe were deposited using a YAG:Nd 3+ laser. The electrical properties of the structures under investigation were analysed on the basis of current–voltage characteristics. These characteristics are interpreted in relation to the structural properties of the Si substrate surface. The carrier transport mechanisms for different HgCdTe/Si interfaces are presented.

Effect of the Si wafer pretreatment on the patterned substrate morphology and growth of Hg1−xCdxTe PLD films

Silicon patterned substrates and Hg 1-x Cd x Te films prepared by pulse laser deposition (PLD) on these substrates were examined by scanning electron microscopy (SEM), electronography (EG) and low-field electroreflectane (ER) spectroscopy in dependence on a pretreatment of Si wafers and the microrelief type. Change in morphologies of the substrates and films is discussed. The crystallinity data and analysis of ER spectra parameters are presented.

PLD of HgCdTe on two kinds of Si substrate

Abstract Films of HgCdTe have been obtained by pulse laser deposition method in dynamic vacuum (pressure∼10 −6 Torr) at 293–543 K. Two different kinds of Si surface were used as substrate: (a) flat standard polished {100} surface and (b) anisotropically chemically etched patterned surface. The results of a scanning electron microscopy investigation, electron probe microanalysis and I – V characteristic measurements showed a strong influence of the substrate kind on the morphology, composition, growth mode, growth defects and transport of HgCdTe/Si heterostructure.

Electrical properties of HgCdTe films obtained by laser deposition

Abstract HgCdTe thin films have been obtained on the Al2O3 surface by the pulse laser deposition method in dynamic vacuum. Films grown at the temperature window of 470–490 K exhibit relatively small electrical resistance. The resistance–temperature characteristics of the films are compared to those of the target and they clearly point to intrinsic and impurity regions. The temperature dependency of the Hall coefficient, the stationary and kinetic photoconductivity of the layers as well as the life time of charge carriers have been studied.

Structural and optical properties of layers of pentacene formed by PLD method

Organic films fabrication offers the possibility of producing electronic devices of low weight, mechanical flexibility and low cost. One suitable material for organic film fabrigation which is the subject of the great interest is pentacene, because it is characterized by the large carrier mobility (∼1 cm2/Vs).In this work, the growth of pentacene layers using pulse laser deposition (PLD) on different substrates (glass/ITO, Si) is described and various processing parameters are investigated. Two pulsed YAG:Nd3+ laser wavelengths were used for the ablation of the PLD target: the first harmonic at 1064 nm aGn:dNdth3+e second at 532 nm. The structure of the layers formed was examined using SEM and RHEED methods. The results were compared with results of optical spectroscopy studies. It will be shown that layers deposed using second harmonics have a higher quality than those for first harmonic. The other PLD parametersalso have a strong influence on the structure quality of layers.

Probe microanalysis investigation and electroreflectance spectroscopy of Hg1−xCdxTe PLD films on silicon patterned substrates

Abstract Hg1−xCdxTe films were prepared on Si-patterned substrates by the pulse laser deposition technique from a Hg1−xCdxTe target (x≈0.2). The effects of different substrate temperatures, ranging from 293 to 543 K, different laser shots number in the range of 10–380, and the morphological type of the patterned substrate on the x-composition of films were studied by electron probe microanalysis (EPMA) and electroreflectance (ER) spectroscopy. The correlation between a film composition measured by EPMA and one determined from ER spectra data was observed.

Optical absorption and reflectivity spectra of highly chromium doped CdTe alloy and layer

In the present work, a CdTe alloy doped with a relatively high concentration of chromium (1%), and a CdTe:Cr layer, have been studied. Absorption and reflectivity spectra were measured at room temperature. They indicate the presence of chromium in the divalent state, both in the alloy and in the layer.

Electrical behaviour of HgCdTe/Si heterostructures

HgCdTe/Si heterostructures (HSs) were obtained by pulsed laser deposition (PLD) on Si (p- or n-type) flat and patterned (pyramid-like and plate-like) substrate from p- or n-type HgCdTe target. The I–V characteristics of p–n and isotype HSs were investigated by the differential approach. This approach is based on monitoring of differential slope α of the I–V characteristics in log–log plot (α=d lgI/d lgV). Influence of the substrate kind (flat, pyramid-like or plate-like), type of conductivity, type of HS (p–n or isotype) and substrate resistivity were studied. In all cases, the main feature of the I–V characteristics behaviour was α=3/2. It means that the bimolecular recombination is the main recombination mechanism in all HSs types.

SEM observation, photoconductivity investigation and I–V study of Si structures with patterned morphology for solar irradiance detection

Abstract Different types of silicon modified patterned substrates with and without p–n-junction were applied as a way for improving solar cells performance in order to prevent the light losses: (i) pyramid like (textured) surfaces (PrS); (ii) hemispherical plate like surface forms (PIS); (iii) dendritic structures (DS); (iv) porous morphology (LEPSi); (v) combinations of a textured surface with a porous one, etc. To realize them the anisotropical chemical and electrochemical etching in various etched mixtures and regimes, epitaxy and ion implantation were performed. Using scanning electron microscopy, spectral photoresponse measurements and current–voltage data, the morphological design, the variations in the photosensitivity, the wavelength peak position and the recombination parameters induced by the patterned processing and their influence for achieving the successful Si solar irradiance detection have been studied and analysed.

Dyson line and modified Dyson line in the EPR measurements

Abstract The difficulty in determining the electron paramagnetic resonance (EPR) line parameters of ferromagnetic semiconductors has been addressed. For these materials, the resonance line is very broad and lies at low resonance field, so that only a part of the line can be detected experimentally. Moreover, the line is of asymmetric (Dysonian) shape as described by the line shape parameter α. We have compared values of line parameters derived by computer fitting of the whole experimental EPR line to the Dyson function (or modified Dyson function) with the values obtained by applying this procedure to the left and the right half of the line.