Abstract This paper is dedicated to preparation and analysis of metal insulator semiconductor (MIS) photoanode with a metal organic chemical vapor deposited RuO2 layer and TiO2 protection layer for photoelectrochemical water splitting. It is shown that utilization of TiO2 layers of 2, 4, and 6 nm thickness preserve the catalytic activity of underlying RuO2. The origin of increased overpotential and decreased photovoltage of the photoanode upon the increase of TiO2 layer thickness is discussed in the paper. Results revealed that utilization of TiO2 layer in the MIS concept is suitable for photoelectrochemical water oxidation applications.

We report on the properties of metal-insulator-semiconductor (MIS) photoanodes for water oxidation employing a thin RuO2-(IrO2) film as a top catalytic layer. In this study, MIS photoanodes with the configurations RuO2/SiO2/n-Si and IrO2-RuO2/SiO2/n-Si were prepared and their photoelectrochemical (PEC) oxygen evolution under solar irradiation has been discussed. The thin SiO2 layers were prepared by the atomic layer deposition method and the RuO2-(IrO2) thin layers were deposited by the metal-organic chemical vapor deposition method. The photocurrent and photovoltage of these MIS photoanodes were studied in 1 M aq. H2SO4 (pH = 0), 0.5 M aq. Na2SO4 (pH = 6), and 1 M aq. KOH (pH = 14) electrolytes showing the trend acidic > alkaline > near-neutral pH conditions for both RuO2- and IrO2-RuO2-based structures. The RuO2/SiO2/n-Si photoanode exhibited a photovoltage of 0.49 V and was able to generate a photocurrent of similar to 10 mA/cm(2) at a thermodynamic water oxidation potential (1.23 V vs the normal hydrogen electrode, NHE) in 1 M aq. H2SO4 solution under 1 Sun intensity with AM 1.5 spectrum. A photovoltage of 0.42 V and a photocurrent of similar to 4 mA/cm(2) were achieved for the IrO2-RuO2/SiO2/n-Si photoanode under acidic conditions. The stability of the photoanodes was examined in 1 M aq. H2SO4 and 1 M aq. KOH solutions. Chronoamperometry measurements on the RuO2/SiO2/n-Si photoanode in acidic solution under an applied voltage of 1.23 V versus NHE showed the deterioration of the photoanode after 2 h of operation. Similarly, stability measurements were performed on IrO2-RuO2/SiO2/n-Si photoanodes in 1 M aq. H2SO4 solution. Under acidic conditions, at an applied bias of 1.23 V versus NHE, a photocurrent of similar to 2 mA/cm(2) was observed, which was stable for 24 h for the IrO2-RuO2-based photoanodes. The preparation, PEC activity, stability, and characterization of the RuO2/SiO2/n-Si and IrO2-RuO2/SiO2/n-Si have been discussed in our study.

The paper presents the results of Deep Level Transient Fourier Spectroscopy (DLTFS) analysis of MOS structures based on a porous p-Si substrate prepared by metal assisted anodic etching. Only three types from five types of samples were appropriate for DLTFS study by their electrical parameters. DLTFS measurements show that metallic contamination occurred in the sample preparation process. The reference, non-etched sample was also subjected to high temperature annealing to form thermal oxide. Au and Zn were confirmed in all DLTFS investigated samples. The impact of anodic etching parameters on defect distribution in the investigated samples is discussed.

The results of capacitive and current voltage measurements on metal-insulator-semiconductor (MIS) photoanode structures with n-type silicon substrate are presented in this paper. The best photo-voltage and photo-current results were obtained on MIS structures with SiO2 grown by Atomic Layer Deposition (ALD). High ideality factor observed in the voltage range 0.1-0.3 V indicates the tunnelling as a dominant transport mechanism through the ALD grown SiO2 layer. Low Flat band voltages confirmed good passivation properties of the prepared ALD grown SiO2. High saturation current and low overpotential of MIS photo-electrochemical structure with ALD SiO2 and RuO2 catalytic layer predict good applicability of ALD prepared passivation layer for light assisted water splitting.

We demonstrate the effect of parallel and antiparallel orientations of spontaneous and piezoelectric polarizations upon the I-V characteristics of vertical metal/GaN/AlGaN/GaN heterostructures. Unlike in the generally accepted model considering parallel orientation of piezoelectric and spontaneous polarization, we achieved reasonable agreement between simulations and experiment only on assuming antiparallel orientation of the two kinds of polarization.

Potentiostatic electrodeposition conducted at various deposition voltages from lactate-stabilized copper sulfate electrolyte was used for preparation of Cu2O layers for Photoelectrochemical (PEC) production of hydrogen. A novel approach based on an application of light during the electrodeposition is utilized to suppress the potential drop in the Cu2O layer during the potentiostatic deposition. Structures prepared under dark and light on an Ag substrate are analyzed by X-Ray Diffraction analysis (XRD), Scanning Electron Microscopy (SEM) and Linear Sweep Voltammetry (LSV). It was shown that the application of light increases the deposition rate due to the contribution of the photogenerated carriers. The deposition voltage affects the photoresponse of light deposited structures but causes only a negligible change in dark deposited structures. The light deposited samples exhibited a higher photoresponse for all deposition voltages. The presented study suggests the light potentiostatic electrodeposition as an attractive approach for the preparation of Cu2O structures for cheap and efficient photoelectrochemical water splitting applications.

We present a high-field electron mobility model of vertical charge transport in Ir/Al /Al2O3/GaN/AlGaN/GaN heterostructures that is, in detail, different from the standard high-field mobility model. The standard model was tailor-made for a 2DEG channel. The wurtzite group-III nitrides GaN and AlN are tetrahedrally coordinated semiconductors with a hexagonal Bravais lattice with four atoms per unit cell. The specific property of this crystal lattice is the induced sheet charge due to spontaneous and piezoelectric polarizations. The sheet charge results in an internal electric field in the crystal lattice. The internal electric field either decelerates or accelerates the vertical electron transport through GaN/AlGaN/GaN heterostructures.

This paper describes fabrication and characterisation of RuO2 based metal-insulator-semiconductor (MIS) structure for photoelectrochemical water splitting. The expected high catalytic activity, transparency, stability and conductivity of RuO2 make this material highly appealing for preparation of a photoanode with high performance. Optical, electrical and photoelectrochemical properties of RuO2 based MIS structures are compared with MIS structures with a Ni catalytic layer. The lower overpotential V-op=0.12 V of RuO2 structure compared to V-op=0.3 V obtained for Ni structure as well as higher saturation photocurrent indicates promising application of the developed RuO2 structures for solar water splitting.

This paper presents an electrical and photoelectrochemical comparison of MIS photoanodes with a metal organic chemical vapor deposited RuO2 layer and evaporated Ni layer to provide a deeper insight into the interface properties of such structures. The unique properties of RuO2 such as high transparency, high conductance, high catalytic activity, and high work function make this material an excellent candidate for a Schottky contact of MIS photoanodes for water splitting. In contrast to the Ni-based MIS structure, no Fermi level pinning was observed when RuO2 was used. This allowed achieving a high measured photovoltage of 0.46 V compared to 0.3 V for a Ni based structure. The ability to achieve the high photovoltage by utilization of RuO2 catalyst is an important achievement for fabrication of high performing MIS structures. (C) 2018 Elsevier B.V. All rights reserved.

The paper presents the results of current and capacitance measurements completed by Deep Level Transient Spectroscopy (DLTS) analysis of MOS structures based on a porous p-Si substrate. On structures prepared by metal assisted anodic etching, parameters were evaluated that represent the degree of the conversion effect of the photovoltaic phenomenon. Under optimal conditions of anodic preparation of the structure, after thermal oxidation and formation of a 14 nm of SiO2 thick layer a photovoltaic response with an open circuit voltage of 0.45 V was recorded.

The contribution employs electrical simulation to assess the effect of the distribution of aluminium in the metal/GaN/AlGaN heterostructure on the leakage current. The heterostructure is characterized by a high density of traps causing an increase of the leakage current consisting of the thermionic emission component and of a non-negligible contribution of trap-assisted tunnelling. The leakage current is highly sensitive to the bending of the potential barrier E-c in the subsurface region of the GaN/AlGaN structure. The band bending is strongly affected by the sheet bound charge at the first GaN/AlGaNIGaN interface due to spontaneous and piezoelectric polarization. The overall charge depends on the concentration of Al, the distribution of Al at the first heterointerface having a strong effect on the formation of the potential barrier. (C) 2016 Elsevier B.V. All rights reserved.

This paper presents an ASA simulation analysis of temperature dependent output parameters of the silicon heterojunction (SHJ) solar cell. The analysis has shown that low temperature behaviors of the open circuit voltage and fill factor are strongly connected with the presence of barriers for collection of photogenerated carriers in the SHJ structure. Previous experimentally observed saturation of the open circuit voltage at low temperature was attributed to the presence of a parasitic Schottky barrier at the transparent conductive oxide/amorphous emitter contact. A comprehensive simulation study is provided to describe the mechanism of such saturation and to define the conditions under which the saturation of the open circuit voltage can be used as relevant identification of the parasitic Schottky barrier in SHJ structures with both n-type and p-type amorphous emitters. In addition, the presented study provides the first guideline on the possible utilization of SHJ in low temperature applications such as space applications. (C) 2016 Elsevier B.V. All rights reserved.

Residual stresses are commonly generated in thin films during the deposition process and can influence the film properties. Among a number of techniques developed for stress analysis, X-ray diffraction methods, especially the grazing incidence set-up, are of special importance due to their capability to analyze the stresses in very thin layers as well as to investigate the depth variation of the stresses. In this contribution a method combining multiple {hkl} and multiple chi modes of X-ray diffraction stress analysis in grazing incidence set-up is used for the measurement of residual stress in strongly textured ZnO thin films. The method improves the precision of the stress evaluation in textured samples. Because the measurements are performed at very low incidence angles, the effect of refraction of X-rays on the measured stress is analyzed in details for the general case of non-coplanar geometry. It is shown that this effect cannot be neglected if the angle of incidence approaches the critical angle. The X-ray stress factors are calculated for hexagonal fiber-textured ZnO for the Reuss model of grain-interaction and the effect of texture on the stress factors is analyzed. The texture in the layer is modelled by Gaussian distribution function. Numerical results indicate that in the process of stress evaluation the Reuss model can be replaced by much simpler crystallite group method if the standard deviation of Gaussian describing the texture is less than 6 degrees. The results can be adapted for fiber-textured films of various hexagonal materials. (C) 2016 Elsevier B.V. All rights reserved.

This paper discusses results of electrically active defect states - deep energy level analysis in InGaAs and GaAsN undoped semiconductor structures grown for solar cell applications. Main attention is focused on composition and growth condition dependent impurities and the investigation of their possible origins. For this purpose a widely utilized spectroscopy method, Deep Level Transient Fourier Spectroscopy, was utilized. The most significant responses of each sample labelled as InG2, InG3 and NG1, NG2 were discussed in detail and confirmed by simulations and literature data. The presence of a possible dual conduction type and dual state defect complex, dependent on the In/N composition, is reported. Beneficial characteristics of specific indium and nitrogen concentrations capable of eliminating or reducing certain point defects and dislocations are stated.

In this article Deep Level Transient Fourier Spectroscopy experiments and various evaluation procedures were used to study emission and capture processes of deep energy levels in intentionally undoped InGaAs and GaAsN semiconductor structures. The examined samples, grown by Atmospheric Pressure Metal Organic Vapour Phase Epitaxy on GaAs substrates, were analyzed at various indium and nitrogen concentrations. Main attention was focused on differences in defect distributions, relations in possible composition and growth condition sensitive defect states. Valuable characteristics of particular In/N contents capable to eliminate or reduce specific impurities are discussed. A possible indium dependent dual state InGaAs complex and a nitrogen and growth condition dependent dual type GaAsN complex was introduced/confirmed. The most balanced samples for further utilizations were achieved for In = 8.9% and N = 1%.

This paper highlights electrical characterization of Schottky structures prepared on AlGaN/GaN designed for HEMT's using Deep Level Transient Fourier Spectroscopy (DLTFS) method with electrical and optical excitation. In case of electrical excitation the density of minority and majority carrier traps had strong effect on the evaluation, whereas preliminary DLTFS with optical excitation (MCDLTFS) measurements made possible to identify minority carrier defects with higher precision. Parameters of two electron-like defects EL1 (0.47 eV), EL2 (0.54 eV) and three hole-like defects HL1 (1.13 eV), HL2 (0.93 eV) and HL3 (0.49 eV) were identified. HL1 andHL2 were confirmed by both methods: DLTFS and MCDLTFS. These are connected to a Carbon interstitial defect and well-know threading dislocations. Experimental results confirmed the benefits of different method utilizations in complex defect identifications.