P.S. Smertenko

Injection technique for the study of solar cell test structures

Abstract Charge carrier injection and recombination processes in semiconductor solar cells is considered and analyzed. A differential approach based on an I–V characteristic approximation is introduced, in order to recognize the mechanisms of injection and recombination and to determine the physical parameters of photovoltaic semiconductor structures. Examples of application of the injection technique for investigation of typical silicon solar cell test structures are demonstrated.

Hafnium dioxide as a passivating layer and diffusive barrier in ZnO/Ag Schottky junctions obtained by atomic layer deposition

This paper reports on ZnO/Ag Schottky junctions obtained by the low temperature atomic layer deposition process. Introducing the thin (from 1.25 to 7.5 nm) layer of hafnium dioxide between the ZnO layer and evaporated Ag Schottky contact improves the rectification ratio to about 105 at 2V. For the ZnO/Ag junctions without the HfO2 interlayer, the rectification ratio is only 102. We assign this effect to the passivation of ZnO surface accumulation layer that is reported for ZnO thin films.

Growth of III–V semiconductor layers on Si patterned substrates

Abstract Patterned unheated Si{100} substrates in the form of the regular tetragonal pyramids and a structure like hemispherical plates have been found to be effective for a pulse vacuum thermal deposition (pulse-VTD) of GaAs and GaP thin layers (50–500 nm). The effect of the pulse-VTD technological parameters (pulse duration, pulse period, pulse number, pulse current) and the features of the substrate patterns (terraces, steps, kinks, sponges) on the morphology, the composition and the crystallinity of GaAs and GaP layers have been characterized by scanning electron microscopy, electron X-ray analysis and electron diffraction.

Simultaneous changes in the photoluminescence, infrared absorption and morphology of porous silicon during etching by HF

Changes in the photoluminescence (PL), microstructural morphology and the chemical nature of the surface of porous silicon (PS) when it is attacked with a 1:1 mixture of concentrated hydrofluoric acid and water have been studied. As the PS dissolves, the porous structure is essentially destroyed while the appearance and chemical composition of the surface change. At the same time, the intensity and peak wavelength of the PL change dramatically. The simultaneous investigation of PL, FTIR absorption and SEM observation of porous silicon layers (PSL) lend support to the view that chemical passivation, in particular by oxygen, is the major factor which controls the origin of PL. The PL intensity and the PL shift are ascribed to the changes in hydrogen and oxygen termination of pores.

Thin films of HgCdTe on silicon surfaces

Thin (about 300 nm and less) HgCdTe and CdTe films have been deposited on Si flat and anisotropically etched microrelief surfaces by YAG:Nd3+ pulsed laser at various substrate temperatures in the range from 323 K to 423 K with 100 laser shots. These films and HgCdTe/Si heterosystems were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and current–voltage characteristics (CVC) analyses. It has been shown that under above conditions laser layer deposition method forms polycrystal films of CdTe, CdHgTe both for microrelief and flat Si substrates in the low temperature range

Deposition of HgCdTe epitaxial layers on anisotropically etched silicon surfaces by laser evaporation

Abstract HgCdTe films have been deposited on Si anisotropically etched microrelief (AEMR) surfaces by YAG:Nd3+ pulsed laser without substrate heating. The formation and a comparative investigation of morphology and some electrophysical properties of HgCdTe films andHgCdTeSi heterosystems on flat and microrelief substrates have been made in dependence on the distance from target to substrate and series of laser pulses. The deposited films and heterosystems were characterized by different techniques: scanning electron microscopy (SEM), micro X-ray electron probe analysis and current-voltage characteristics method. Based on these data it has been shown that the film growth process on Si AEMR surface in the morphological stability conditions (films reproduce the substrate microrelief) is the result of layer by layer mechanism with step migration and without nucleation. The difference in current-voltage characteristics are discussed in term of injection phenomena and depends strongly on laser deposition conditions.

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.

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.

Some properties of thin film structures on the base of ZnO obtained by MOCVD method

The ZnO thin film structures were obtained by MOCVD method under atmospheric pressure onto Si substrates heated up to 250-350 оС. The film thickness varied from 0.4 – 0.5 µm. The phase composition, structure and morphology of ZnO films as well as electrophysical properties of ZnO/Si heterojunction on their base were investigated. The possible charge flow mechanisms in ZnO/Si heterojunction are discussed.

Synthesis and Properties of Hybrid Poly(3-Methylthiophene)-CdSe Nanocomposite and Estimation of Its Photovoltaic Ability

We report the synthesis and properties of new hybrid nanocomposites of poly(3-methylthiophene) and CdSe nanoparticles. The synthesis method is based on the chemical oxidative polymerization of 3-methylthiophene in the presence of CdSe nanoparticles of different shapes (quantum dots, nanorods, and tetrapods). In situ, the open circuit potential and the UV-Vis monitoring of a reaction mixture are used to control the polymerization process. The minimal and maximal CdSe concentrations in nanocomposites are obtained for quantum dots and nanorods, respectively. Nanocomposites are investigated, by using IR, electronic absorption, and photoluminescence spectroscopies, TGA, and DTA. Hybrid photovoltaic (PV) cells based on these materials are fabricated and evaluated. The best PV performance is achieved for a device based on nanocomposites with CdSe nanorods.