Characterization of non-homogenously doped semiconductor epilayers requires specialized equipment and complex research approach that focuses in particular on the analysis of the dopant profile varying in a gradient along the epitaxial layer. In the case of such structures, precise knowledge of the dopant level, its distribution profile, and layer thickness is crucial. These parameters have a tremendous impact on performance of many optoelectronic devices, for instance quantum cascade lasers. This paper analyses and compares the measurement results of gradually silicon doped indium phosphide epilayers InP:Si examined and cross checked by different methods as the electrochemical capacitance-voltage profiling, atomic force microscopy and secondary-ion mass spectrometry. We analysed InP epitaxial layers deposited by LP-MOVPE (Low Pressure MetalOrganic Vapour Phase Epitaxy) technique with medium doping in the range of k pound 1016 to k pound 1017 cm-3 as well as heavily doped layers with electron concentration exceeding k pound 1019 cm-3. Finally, we have found a simple, linear relationship between the silicon ions related signal measured by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and free electron concentration determined by EC-V method. Moreover, based on the AFM investigations we did not observe degradation of the InP surface induced by modulation of the doping profile shape.

Gallium oxide (Ga2O3) is a promising semiconductor material for high-power electronics; however, its low thermal conductivity is a challenge for the device performance and reliability. To address this issue, heteroepitaxial beta-Ga2O3 thin films were grown on highly-thermally-conductive 4H-SiC substrates using liquid-injection MOCVD and subjected to H-containing annealing at different temperatures to enhance their conductivity. The MOSFET devices processed on Si-doped beta-Ga2O3 films were annealed at identified optimal temperature of 550 degrees C, and showed output current of 0.8 mA/mm, ON/OFF current ratio of similar to 10(6), and breakdown voltage of 150 V. Using structural, compositional, and electrical characterization of the films and devices, observed resistivity drop was attributed to H passivation of the compensating acceptor centers, possibly via formation of Ga-vacancy-hydrogen complexes. Low MOSFET output current was proposed to originate from nearest-neighbor hopping conduction with the activation energy of similar to 141 meV. We propose the observed transport mechanism is a result of structural disorder introduced by O vacancies or Si-OH complexes. Further, another deeper donor with energy level of similar to 69 meV was identified and assigned to Si atom occupying octahedrally-coordinated Ga site.

Perovskite solar cells (PSCs) experience significant photovoltage losses due to nonradiative recombination, especially in p-i-n devices with Fullerene C60 as the electron transport layer (ETL), which limits device performance. To tackle this issue, we propose a strategy that synergistically suppresses nonradiative recombination at the perovskite/C60 interface by employing a 2D heterointerface with a two-site anchor bridge, which reduces the surface defect density. This process elevates the fermi level and enhances the electric field, facilitating electron extraction at the perovskite/C60 heterointerface. As a result, nonradiative recombination at this electron-selective perovskite contact is greatly suppressed. p-i-n PSCs fabricated using this interface engineering approach achieved a power conversion efficiency (PCE) of 26.32% and demonstrated excellent stability under continuous maximum power point tracking, along with an open-circuit voltage (Voc) of 1.217 V. This broadly applicable and scalable approach further delivers an impressive Voc of up to 1.368 V in wide-bandgap (1.8 eV) devices. Overall, the strategy offers a viable pathway toward efficient and stable inverted PSCs, demonstrating broad compatibility with diverse perovskite compositions.

Monolithic perovskite–organic tandem solar cells (P–O TSCs) establish a mutual protection system, which enables high-efficiency P–O TSCs (25.12%) to achieve exceptional operational stability, retaining over 91% after 1000-hour illumination.

Ligand engineering is an effective method to reduce defects in perovskite solar cells (PSCs) and to enhance efficiency. Likewise, enhancing device stability through ligand engineering is currently emerging as a key focus to suppress the bidirectional migration of halides and silver ions, which otherwise can cause irreversible chemical corrosion to the electrode and perovskite layer. Here, triphenylphosphine oxide (TPPO) is demonstrated to improve the long-term operational stability of PSCs when introduced at the interface between the perovskite and the electron transport layer (ETL). TPPO effectively eliminates uncoordinated Pb2+ and thus reduces surface defects. Accordingly, the target solar cell yields a hero power conversion efficiency (PCE) of 26.01% and a maximum open-circuit voltage (VOC) of 1.23 V, representing the minimum voltage deficit (0.32 V) reported for methylammonium-free (MA-free) PSCs. Moreover, long-term operational analysis reveals that the bidirectional migration of halides and silver ions is significantly suppressed, resulting in enhanced device stability. TPPO-modified PSCs retain 90% of the initial PCE after 1200 hours of operation in maximum power point tracking. Ligand engineering with TPPO marks a significant advancement in enhancing the stability of PSCs and is fully compatible to upscaling scenarios.

Boron-doped diamond (BDD) films are becoming increasingly popular as electrode materials due to their broad potential window and stability in harsh conditions and environments. Therefore, optimizing the crystal quality and minimizing defect density to maximize electronic properties (e.g. conductivity) of BDD is of great importance. This study investigates the influence of different hydrogenated nanodiamond (H-ND) seeding layers on the growth and properties of BDD films. Three types of seeding H-NDs were examined: detonation (H-DND) and topdown high-pressure high-temperature NDs (TD_HPHT H-ND), and boron-doped NDs (H-BND) newly synthesized at high-pressure high-temperature from an organic precursor. Purified and oxidized BND (O-BND) samples yielded clear, blue, and stable colloidal dispersions. Subsequent thermal hydrogenation reversed their zeta potential from - 32 mV to +44 mV and promoted the seeding of negatively charged surfaces. All three H-ND types formed dense seeding layers on SiO2 and Si/SiOx substrates, which enabled the growth of BDD films by chemical vapor deposition (CVD). Despite variations in initial surface coverage among the seeding layers (13-25 %), all NDs facilitated the growth of fully closed BDD films approximately 1 mu m thick. Significant differences in film morphology and electrical properties were observed. H-BND nucleation yielded the BDD films with the largest crystals (up to 1000 nm) and lowest sheet resistance (400 Omega/sq). This superior performance is attributed to the uniform particle shape and monocrystalline character of H-BND, as corroborated by FTIR, TEM, and SAXS measurements. These findings highlight the critical role of seeding layer properties in determining consequent diamond film evolution and establish H-BNDs as promising seeding material for the growth of high-quality BDD films suitable for electronic and electrochemical applications.

Three-dimensional/two-dimensional (3D/2D) heterojunctions in perovskite solar cells exhibit excellent optoelectronic properties and enhanced stability under mild ageing conditions. However, their performance degrades drastically under harsh ageing conditions. This study reveals the intrinsic instability of mono-ammonium based 2D perovskites (2D-mono) under photo-thermal ageing, which decompose into PbI2 and metallic lead (Pb0). The structural collapse promotes vacancy formation and facilitates iodide migration to the anode. As a result, it triggers a redox reaction that reduces the transport layer's mobility and doping concentration, leading to a significant increase in series resistance. Compared to mono-ammonium-2D structure, di-ammonium-2D (2D-di) based interfaces demonstrate superior structural stability and effectively block iodide migration into the transporting layer. However, blocking-induced uneven iodide distribution leads to interstitial defect formation in the 3D layer, exacerbating non-radiative recombination. To address it, we propose a strategical method by incorporating 2D-di in the 3D bulk instead of on the top surface, which effectively confines mobile ions within the grain and suppresses cation phase segregation. This optimization yields stable perovskite solar cells with an extrapolated operational T80 lifetime exceeding 560 hours under harsh conditions (85 degrees C and 2-sun illumination). Three-dimensional/two-dimensional (3D/2D) heterojunctions in perovskite solar cells exhibit excellent optoelectronic properties and enhanced stability under mild ageing conditions.

Nanostructured boron-doped diamond (BDD) offers a sizeable ion-accessible area, high mechanical robustness, and high electrical conductivity, and could be a suitable electrode for high-performance electrochemical (EC) supercapacitors. Herein, two morphological BDD films, namely, boron-doped microcrystalline diamond (BMCD) and boron-doped ultra-nanocrystalline diamond (BUNCD), are employed for nanostructuring. The diamond nanopillars are fabricated via the Au mask-assisted reactive ion etching (RIE) method. The nanostructured samples of BMCD and BUNCD are termed BMCDN and BUNCDN. The Raman spectroscopy and X-ray photoelectron spectroscopy measurements of these nanostructured samples confirm the presence of sp2 in sp3-bonded carbon, which combine to offer good EC activity of sp2 and exceptional stability of sp3 carbon. These nanostructured BDD samples with enhanced surface area are utilized as electrode materials to construct an electric double-layer capacitor and pseudocapacitor. In 1 M Na2SO4 solution, the maximum specific capacitance of BMCDN is found to be 0.0852 mF cm-2, whereas, for BUNCDN the value is 0.0784 mF cm-2. The electrochemical analysis of these samples shows they exhibit superior electron transfer kinetics with 80% capacitance retention after 2000 cycles, which indicates the suitable utilization of these nanostructured samples as electrodes in EC supercapacitors. Nanostructuring boron-doped diamond effectively improves the electrochemical supercapacitor performance with high lifetime stability.

Mixed lead and tin (Pb/Sn) hybrid perovskites exhibit a great potential in fabricating all‐perovskite tandem devices due to their easily tunable bandgaps. However, the energy deficit and instability in Pb/Sn perovskite solar cells (PSCs) constrain their practical applications, which renders defect passivation engineering indispensable to develop highly efficient and long‐term stable PSCs. Herein, the mechanisms of strain tailoring and defect passivation in Pb/Sn PSCs by 2D ligands are investigated. The 2D ligands include electroneutral cations with long alkyl chain (LAC), iodates with relatively short alkyl chain (SAC) and their mixtures. This study reveals that LAC ligands facilitate the relaxation of tensile strain in perovskite films while SAC ligands cause strain buildup. By mixing LAC/SAC ligands, tensile strain in perovskite films can be balanced which improves solar cell performance. PSCs with admixed β ‐guanidinopropionic acid (GUA)/phenethylammonium iodide (PEAI) exhibit enhanced open circuit voltage and fill factor, which is attributed to reduced nonradiative recombination losses in the bulk and at the interfaces. Furthermore, the operational stability of PSCs is slightly improved by the mixed 2D ligands. This work reveals the mechanisms of 2D ligands in strain tailoring and defect passivation toward efficient and stable narrow‐bandgap PSCs.

Metal organic chemical vapor deposition was used to grow N-polar In0.63Al0.37N on sapphire substrates. P-doping was provided by a precursor flow of Cp2Mg between 0 and 130 nmol/min, reaching a Cp2Mg/III ratio of 8.3 × 10−3. The grain structure of 360 nm thick InAlN was spoiled by pits after introducing a flow of CP2Mg at 30 nmol/min. The surface quality was improved with a flow of 80 nmol/min; however, detrimental deterioration appeared at 130 nmol/min. This correlated with the XRD shape and determined density of dislocations, indicating a phase separation at the highest flow. Degenerated n-type conduction and a free carrier concentration of ~1019 cm−3 were determined in all samples, with a minor compensation observed at a CP2Mg flow of 30 nmol/min. The room temperature (RT) electron mobility of ~40 cm2/Vs of the undoped sample was reduced to ~6 and ~0.3 cm2/Vs with a CP2Mg flow of 30 and 80 nmol/min, respectively. Scattering at ionized acceptor/donor Mg-related levels is suggested. RT photoluminescence showed a red shift of 0.22 eV from the virgin 1.73 eV peak value with Mg doping. Mobility degradation was found to be the main factor by InAlN resistivity determination, which increased by two orders of magnitude, approaching ~0.5 Ωcm, at the highest Cp2Mg flow.

In this paper, the analysis of silicon oxynitride (SiON) films, deposited utilizing the plasma enhanced chemical vapor deposition (PECVD) process, for optical waveguides on silicon wafers is presented. The impact of N2O flow rate on various SiON film properties was investigated. The thickness and refractive index were measured by micro-spot spectroscopic reflectometry and confirmed by spectroscopic ellipsometry. The chemical composition of SiON films was analyzed using Secondary Ion Mass Spectrometry (SIMS). The surface roughness was analyzed using Atomic Force Microscopy (AFM). Increasing the N2O flow rate during deposition caused the deposition rate to increase and the refractive index to decrease. By changing the flow rate of gases into the chamber during the PECVD process, it is possible to precisely adjust the oxygen (O-2) ratio and nitrogen (N-2) ratio in the SiON film and thus control its optical properties. This was possibility utilized to fabricate SiON films suitable to serve as a waveguide core for optical waveguides with a low refractive index contrast.

The effect of silicon oxynitride (SiON) layer on the thermally-induced stress of diamond-coated AlGaN/GaN heterostructures was studied by Raman and SIMS spectroscopy. Diamond films (0.8 or 2.8 mu m in thickness) were grown by MWCVD on selected areas of AlGaN/GaN/Si substrates with SiON interlayer. The stress in diamond became tensile for the thinner strip in the range of 0 - 0.5 GPa and compressive for the thicker strip in the range of -0.6 - -0.1 GPa both measured at temperatures ranging from 50 to 400 degrees C. The applied SiON interlayer positively influenced the induced stress (Delta stress decreased by about 0.14 GPa compared to the sample without SiON) independently on the thickness of the diamond film. SIMS depth profiling was applied to analyse the influence of diamond CVD on the AlGaN/GaN interface of SiON passivated samples. As observed, the hydrogen and carbon atoms were trapped in the SiON which acted as a stop layer.

Pulsed laser deposition (PLD) is a deposition method which provides some special advantages in comparison with other traditional technologies used for thin films growth. One of them is ability to deposit thin films in wide range of composition on different substrates regardless of their chemical, electrical, mechanical or geometrical properties. The presented work deals with deposition of thin ZnO based coating layers on GaP nanorods. The layers were grown by using of PLD and the goal was to prepare a homogenous and continuous shell layer on GaP substrate as well as on GaP nanorods. The results showed that ZnO layers prepared on GaP nanorods exhibited homogenous thickness which can be controlled by the deposition time (the number of deposition pulses). On the other side, the method is sensitive on orientation of nanorods against the deposition plasma plume direction. The acquired results proved that PLD could serve as a promising deposition method for this presently frequent kind of task ? homogenous coating of intricate nanostructured surfaces.

g5rt Samples comprising 1.3 mu m-thick C-doped semi-insulating (SI) GaN layer sandwiched between two n-GaN layers were grown on sapphire or conductive GaN substrates by metal-organic chemical vapor phase epitaxy at varied reactor pressure between 100 and 20 mbar. Vertical cylindrical resistors with a radius of 50 mu m were defined by similar to 1.6 mu m-deep mesa etching down to the bottom Si-doped n-GaN layer. X-ray diffraction rocking curves revealed almost invariant crystallographic quality of homo-epitaxial structures grown on the GaN substrate, while dislocations in GaN on sapphire lead to curve broadening and pits formations. C concentration in SI GaN grown on the GaN substrate was found to increase from similar to 1. 10(17) cm(-3) to similar to 6 x 10(18) cm(-3)as the growth pressure decreased from 100 mbar to 20 mbar. However, one order of magnitude lower C concentration and inhomogeneous distribution was found for the sapphire substrate. I-V characterization showed that the electrical strength of SI GaN could be as high as 2.8 MV/cm if grown at 20 mbar on the GaN substrate. In this case the nondestructive break-down voltage exceeds 350 V with a positive T coefficient pointing on impact ionization. Sample grown on the GaN substrate at 20 mbar demonstrated ln(I) similar to V dependence which is typical for a barriercontrolled leakage. Extracted barrier height of 0.41 eV at the n-GaN/SI GaN interface was explained by C-related compensation effect and by a shifting of the Fermi level. On the other hand, apart from SI GaN grown on GaN substrate at 20 mbar, all other structures showed I = f(V-n) dependence indicating a space-charge-limited current conduction mechanism. It is suggested that the optimized SI GaN grown on GaN substrate can be considered as a current blocking layer or as a channel in robust geometry vertical transistors.

The unique properties of boron-doped diamond make it a promising electrode material for electroanalytical applications, especially for stripping voltammetry. The boron-doped diamond (BDD) electrodes prepared by chemical vapor deposition (CVD) on alumina substrates were electrochemically characterized by cyclic voltammetry. The influence was investigated of the boron dopant concentration, surface termination as well as chemical surface treatment on the kinetics of the electrode reaction. A standard redox couple, ferro/ferricyanide in aqueous solution, was employed to determine important kinetic parameters (anodic transfer coefficient, diffusion coefficient, and electron transfer rate constants) of the reaction. The effect of surface conditions of the boron-doped diamond electrodes on the kinetics of the electrodeposition of bismuth film was investigated for electrochemical applications in which bismuth film electrodes are utilized. A favourable effect of the cleaning procedures was proved, especially for the oxygen plasma-treated BDD electrode with a higher content of boron in alkaline solution. The anodic current response was increased by 109% when compared with as-grown BDD. The effect of the quality of bismuth film on analytical performance of the voltammetric sensor was verified in simultaneous analysis of heavy metals (Pb, Cd and Zn) by anodic stripping voltammetry.

The contribution deals with growth of ZnO nanowires on metal catalysts by using of pulsed laser deposition and with the influence of growth temperature. The process of nanowires preparation comprised two technological steps—both were based on pulsed laser ablation processes: (1) production of metal nanoparticles by laser ablation in liquids and (2) pulsed laser deposition of ZnO nanowires by ablation of ZnO target on substrate with metal nanoparticles. Nanoparticles from various metals (Au, Ag, Ni, Cu, Al, Mg, Zn, Sn and BiSn alloy) were prepared by pulsed laser ablation at 1064 nm in deionised water. Colloids contained metal nanoparticles were applied on Si (100) substrates, and after drying, nanoparticles served as catalysts of VLS crystallisation. Temperatures in interval 600—200 °C were experimentally compared for the nanowires growth with applied ablation laser working at 248 nm. The lowest achieved temperature value for growth of ZnO nanowires was 425–450 °C. However, among applied metals Cu and Al nanoparticles only successfully catalysed ZnO nanowires at this temperature. Properties of prepared samples were investigated by scanning electron microscopy and photoluminescence. Experimental results revealed that along with the growth temperature, selection of proper metal catalyst is also important factor for nanowires crystallisation.

The contribution deals with Ga doped ZnO films (deposited from a sintered target composed of 99.0 ZnO and 1.0 wt % of Ga2O3) prepared by pulsed laser deposition (PLD). Experimentally were compared the deposition parameters influence on structural, optical and electrical properties. The variable parameters were: deposition temperature (RT to 500 degrees C) and growth rate (controlled by laser pulsing repetition frequency in range 2-50 Hz). Investigation by SEM and XRD confirmed columnar structure of prepared films with highly uniform crystal-lographic orientation regardless of applied deposition parameters. Samples exhibited high optical transparency in VIS region with sharp absorption edge near 380 nm and band gap energies varied between 3.19 and 3.24 eV at room temperature. The best electrical properties (resistivity similar to 5.96 x 10(-4) Omega cm) was achieved at 400 degrees C and 10 Hz of laser frequency, however the application of deposition at RT or highest laser frequency (50 Hz) still maintain average resistivity at levels of 10(-3) Omega cm. The results suggest that PLD can play an important role in production of high conductive transparent thin film deposited on temperature sensitive organic materials at RT deposition levels.

The surface nanostructuring of boron doped diamond (BDD) can further enhance its unique properties e.g. in electrochemical sensing, photoelectrochemical cells, field emission devices and various kinds of sensors. Here we present an investigation of plasmatic nanostructuring of BDD films without use of a time-consuming masking process. RF plasma technique was used to etch surface nanostructures with dimensions ranging from tenths to hundreds of nm in width and height. The size and shape of achieved diamond nanostructures were influenced only by applied etching parameters. We have found that the etched carbon is re-deposited in an amorphous form creating a mask and this self-masking process is responsible for the final shape of obtained structures. Therefore, this technique is effectively controllable by changing plasma power, gas type and pressure which influence the energy of incident ions and thus the sputtering yield and re-deposition of masking material. Utilization of various gas types, pressures and RF powers revealed the physical type of etching to be dominant over the chemical at both high and low energy ions. The nanostructured surfaces were then observed and characterized by SEM and Raman spectroscopy to investigate the nanostructures dimensions and to confirm the remaining diamond quality.

In this work we present approach that allows regrowth of AlGaN/GaN heterostructures on plasma etched GaN templates without occurrence of buried conductive layer. Discussion about the influence of RIE (reactive ion etching) process on the properties of GaN surface is followed by presentation of experimental work results focused on reconstruction of GaN template surface after etching in chlorine plasma in order to growth AlGaN/GaN heterostructure without parasitic channel. Analysis of GaN surface treatment after RIE process using 10% aqueus HF solution and low temperature GaN (LT-GaN) nucleation layer is carried out, including SEM (scanning electron microscopy) imaging and SIMS (secondary ion mass spectroscopy) profiling. The AlGaN/GaN heterostructures with the thickness as low as 250 nm deposited on plasma etched GaN templates with sheet resistance under 600 Omega/square and good uniformity were fabricated using this approach. Presented method can be used in fabrication of current aperture vertical electron transistor (CAVET) structures with low leakage currents.