Dopant Diffusion Research Articles

Сравнительное исследование фотоэлементов на основе кремния, легированного никелем различными методами

In this work, the parameters of silicon-based photocells doped with impurity nickel atoms by diffusion methods and during growth were compared. It was found that photocells doped with impurity nickel atoms during silicon growth have an improvement in parameters comparable to that obtained by the diffusion doping method. Additional heat treatment at T = 800 °C makes it possible to significantly improve their basic parameters.

Радиационная стойкость кремниевых солнечных элементов, легированных никелем

The influence of nickel doping on the radiation resistance of silicon solar cells in the range of γ-irradiation doses of 10^5–10^8 rad was studied. It is shown that diffusion doping of silicon with impurity nickel atoms increases the radiation resistance of the parameters of silicon solar cells. It is assumed that the reason for the increase in the radiation resistance of such solar cells is the existence of clusters of impurity nickel atoms, which serve as sinks for radiation defects.

Efficient and Stable Perovskite Solar Cells Based on Inorganic Hole Transport Materials.

Although power conversion efficiencies of organic-inorganic lead halide perovskite solar cells (PSCs) are approaching those of single-crystal silicon solar cells, the working device stability due to internal and external factors, such as light, temperature, and moisture, is still a key issue to address. The current world-record efficiency of PSCs is based on organic hole transport materials, which are usually susceptible to degradation from heat and diffusion of dopants. A simple solution would be to replace the generally used organic hole transport layers (HTLs) with a more stable inorganic material. This review article summarizes recent contributions of inorganic hole transport materials to PSC development, focusing on aspects of device performance and long-term stability. Future research directions of inorganic HTLs in the progress of PSC research and challenges still remaining will also be discussed.

Cr-doped ZnGa2O4: Simple synthesis of intense red-NIR emitting nanoparticles with enhanced quantum efficiency

Red-NIR emitting ZnGa2-xCrxO4 nanoparticles were synthesized using simple co-precipitation, and the effect of annealing was studied (600–1200 °C). Upon annealing, crystallite size increased (12 nm–73 nm), and color tone turned pink beyond 1000 °C, inferring dopant diffusion. Blue, green absorption bands in diffuse-reflectance spectra revealed Cr3+ in octahedral crystal field. Photoluminescence excitation spectra showed characteristic Cr3+ bands (∼400 nm and ∼550 nm), and the asymmetric 400 nm band suggested splitting the 4T1g(F) state due to trigonal distortion. Emission spectra consisted of a zero-phonon line (∼688 nm), along with associated multi-phonon sidebands. ZnGa1.98Cr0.02O4 showed intense red emission with λexc = 420 nm, while the tri-exponential fitting of the excited-state lifetime implied multiple decay processes due to Cr3+ occupying different environments. The internal quantum efficiency of the 1200 °C annealed sample was impressive (48%). Both UV and visible light up to 600 nm could induce persistent-luminescence (λem = 688 nm) for longer durations. The smaller size, intense emission, higher quantum yield, and visible light activation suggest that the nanoparticles are suitable for bioimaging applications.

Silicon‐based passivating contacts: The TOPCon route

AbstractPassivating contacts based on poly‐Si/SiOx structures also known as TOPCon (tunnel oxide passivated contacts) have a great potential to improve the efficiency of crystalline silicon solar cells, resulting in more than 26% and 24% for laboratory and industrial cells, respectively. This publication gives an overview of the historical development of such contact structures which have started already in the 1980s and describes the current state‐of‐the‐art in laboratory and industry. In order to demonstrate the great variety of scientific and technological research, four different research topics are addressed in more detail: (i) the superior passivation quality of TOPCon structures made it necessary to re‐parametrize intrinsic recombination in silicon, (ii) the control of diffusion of dopants through the intermediate SiOx layer is essential to optimize passivation and transport properties, (iii) single‐sided deposition of the poly‐Si layer would reduce process complexity for industrial TOPCon cells, and (iv) silicon‐based tunnel junctions for perovskite–silicon tandem cells can be fabricated using the TOPCon technology.

Cross-Linking of Doped Organic Semiconductor Interlayers for Organic Solar Cells: Potential and Challenges

Solution-processable interlayers are important building blocks for the commercialization of organic electronic devices such as organic solar cells. Here, the potential of cross-linking to provide an insoluble, stable, and versatile charge transport layer based on soluble organic semiconductors is studied. For this purpose, a photoreactive tris-azide cross-linker is synthesized. The capability of the small molecular cross-linker is illustrated by applying it to a p-doped polymer used as a hole transport layer in organic solar cells. High cross-linking efficiency and excellent charge extraction properties of the cross-linked doped hole transport layer are demonstrated. However, at high doping levels in the interlayer, the solar cell efficiency is found to deteriorate. Based on charge extraction measurements and numerical device simulations, it is shown that this is due to diffusion of dopants into the active layer of the solar cell. Thus, in the development of future cross-linker materials, care must be taken to ensure that they immobilize not only the host but also the dopants.

Probing Relaxation Dynamics and Stepped Domain Switching in Boron‐Alloyed VO2

AbstractThe characteristic metal–insulator phase transition (MIT) in vanadium dioxide results in nonlinear electrical transport behavior, allowing VO2 devices to imitate the complex functions of neurological behavior. Chemical doping is an established method for varying the properties of the MIT, and interstitial dopant boron has been shown to generate a unique dynamic relaxation effect in individual B‐VO2 particles. This paper describes the first demonstration of an electrically stimulated B‐VO2 proto‐device which manifests a time‐dependent critical transformation temperature and switching voltage derived from the coupling of dopant diffusion dynamics and the metal–insulator transition of VO2. During quasi‐steady current‐driven transitions, the electrical responses of B‐VO2 proto‐devices show a step‐by‐step progression through the phase transformation, evidencing domain transformations within individual particles. The dynamic relaxation effect is shown to increase the critical switching voltage by up to 41% (ΔVcrit = 0.13 V) and also to increase the resistivity of the M1 phase of B‐VO2 by 14%, imbuing a memristive response derived from intrinsic material properties. These observations demonstrate the dynamic relaxation effect in B‐VO2 proto‐devices whose electrical transport responses can be adjusted by electronic phase transitions triggered by temperature but also by time as a result of intrinsic dynamics of interstitial dopants.

Numerical Investigation of the Effects of the Beam Scanning Pattern and Overlap on the Temperature Distribution during the Laser Dopant Activation Anneal Process

Laser thermal annealing (LTA) has played an important role in the fabrication of scaled semiconductor devices by reducing the heat budget of the dopant activation process. During the laser annealing of entire wafer areas, the beam scanning pattern and overlap ratio have significant effects on uniform heating during the process. In this study, a numerical simulation of the LTA process was carried out using a three-dimensional transient heat transfer model. The temperature distribution produced by different laser scan paths and beam overlap ratios was analyzed. Additionally, the behavior of the dopant (phosphorus) diffusion induced under the multipath and beam overlapping conditions was numerically investigated. According to the simulation result, a zig-zag pattern generated hot spots around the corner areas of the beam path due to the greater heat accumulation per unit area; however, a bidirectional pattern induced cold spots due to the absence of laser heating around the corner areas. It was also found that the maximum temperature reachable in the beam overlapped region was much lower than that obtained along the beam scanning path, and the most uniform heating could be obtained when the zig-zag pattern and a 50% overlap ratio were used. According to the dopant diffusion and concentration distribution predicted for the case of the zig-zag pattern and 50% overlap ratio, the difference in the dopant diffusion length was approximately thirty times within the scanned area.

A Review of the Reliability of Integrated IR Laser Diodes for Silicon Photonics

With this review paper we provide an overview of the main degradation mechanisms that limit the long-term reliability of IR semiconductor lasers for silicon photonics applications. The discussion is focused on two types of laser diodes: heterogeneous III–V lasers bonded onto silicon-on-insulator wafers, and InAs quantum-dot lasers epitaxially grown on silicon. A comprehensive analysis of the reliability-oriented literature published to date reveals that state-of-the-art heterogeneous laser sources share with conventional laser diodes their major epitaxy-related degradation processes, such as the generation of non-radiative recombination centers or dopant diffusion, while eliminating cleaved facets and exposed mirrors. The lifetime of InAs quantum dot lasers grown on silicon, whose development represents a fundamental step toward a fully epitaxial integration of future photonic integrated circuits, is strongly limited by the density of extended defects, mainly misfit dislocations, protruding into the active layer of the devices. The concentration of such defects, along with inefficient carrier injection and excessive carrier overflow rates, promote recombination-enhanced degradation mechanisms that reduce the long-term reliability of these sources. The impact of these misfits can be largely eliminated with the inclusion of blocking layers.

Optical characterization of a neodymium-doped lithium-niobate-on-insulator (LNOI)

A neodymium (Nd) doped lithium-niobate-on-insulator (LNOI) was fabricated from a lithium niobate (LN) substrate diffusion-doped with Nd prior to the LNOI fabrication process. Diffusion doping enables the fabrication of differently doped regions on a single LNOI substrate, a key advantage for future applications in highly integrated photonics. Fluorescence spectra, emission cross-section, fluorescence lifetime, and small-signal gain of Nd:LNOI were determined for the first time to our knowledge and compared with data published for diffusion-doped ridge or channel waveguides in LN substrates. For an 11 mm-long sample, we achieve a small-signal gain for π (σ) polarization of about 14 (10) dB when pumping with a Ti:Sapphire laser, which is promising for future active components in Nd:LNOI like amplifiers and lasers.

Single and Dual Doping of Blue‐Emissive ZnSeTe Quantum Dots with Transition Metal Ions

AbstractDoping particularly with transition metal ions is an effectual means to modulate photoluminescence (PL) of quantum dots (QDs). The precedent doped QDs rely primarily on single doping with either Cu+ or Mn2+ into the most common host compositions of (Zn)CdS, ZnSe, and InP, with little success on co‐doping with both impurities enabling their simultaneous emissions. Herein, single and dual doping are explored with Cu+ and/or Mn2+ into blue‐emissive ZnSeTe QDs. PL of the singly doped ZnSeTe QDs synthesized via a co‐nucleation process, comprising host and dopant emissions, is spectrally tuned by varying the concentration of each dopant. For the effective dual doping toward co‐emergence of both dopant‐related emissions, a two‐step doping strategy, where co‐nucleation doping of Mn2+ is temporally decoupled from diffusion doping of Cu+, is devised. In the resulting co‐doped ZnSeTe QDs, successfully showing three distinct emission components, the relative spectral distribution of triple emissions is readily modulated by individually adjusting Cu and Mn concentrations, producing color‐quality tunable white emissions. Upon elaborate multishelling, the co‐doped QDs display outstanding PL quantum yields of 72–75%. Singly and dually doped QDs are further applied for the fabrication of QD light‐emitting diodes, and their electroluminescence is examined compared to PL.

Surface Polarization Doping in Diketopyrrolopyrrole-Based Conjugated Copolymers Using Cross-Linkable Terpolymer Dielectric Layers Containing Fluorinated Functional Units.

It is essential to tune the electrical properties of inorganic semiconductors via a doping process in the fabrication of cutting-edge electronic devices; however, the doping in organic field-effect transistors (OFETs) is limited by the uncontrollable dopant diffusion and low doping efficiencies. This study proposes the use of a fluorinated functional group in a polymer dielectric layer as an effective p-type doping strategy for ambipolar diketopyrrolopyrrole (DPP)-based donor-acceptor (D-A)-type semiconducting copolymer films used in OFETs, without generating structural perturbations. To experimentally verify the surface polarization doping effect of the fluorinated group, two terpolymers─poly(pentafluorostyrene-co-3-azidopropyl-methacrylate-co-propargyl-methacrylate) (5F-SAPMA), wherein fluorinated units are included, and poly(phenyl-methacrylate-co-3-azidopropyl-methacrylate-co-propargyl-methacrylate) (PhAPMA), without fluorinated units─are designed and synthesized for use in OFETs. The synthesized 5F-SAPMA and PhAPMA films were cross-linked through the click reaction between the alkyne and azide units in the terpolymers at 150 °C to provide chemical, thermal, and mechanical stabilities and solvent resistance. The electrical characterization of the OFETs with the newly synthesized terpolymer dielectrics reveals that the surface polarization induced by the fluorinated groups of the 5F-SAPMA dielectrics leads to the generation of additional hole charges and helps minimize the broadening of the extended tail states in the vicinity of the valence band (highest occupied molecular orbital (HOMO) level). This not only enables a transition from the ambipolar to p-type dominant characteristics but also helps increase the hole mobility from 0.023 to 0.305 cm2/(V·s).

The Mechanism of Surface Passivation Degradation in SiO2/SiNx Stack Under Light and Elevated Temperature

In this article, a significant degradation of the surface passivation was observed in Czochralski silicon (Cz-Si) lifetime samples using effective lifetime measurements during 1 sun illuminated treatment at 130 °C–175 °C. The samples are passivated by plasma-enhanced chemical vapor deposited silicon nitride (SiNx) and thermally grown silicon oxide (SiO2). Samples showed strong variations in the kinetics of the surface passivation degradation depending on the passivation stacks, phosphorus diffusion, and bulk doping. Recovery of the surface passivation was only observed on samples passivated by a single silicon nitride layer. To further investigate the observed behavior, corona charging capacitance-voltage measurements were performed. It is shown that surface degradation arises from a combination of changes in interface defect density ( Dit ) and fixed charge density ( Qf ). We show that two separate degradation channels contribute to the degradation in surface passivation, where the fixed charge density continuously declines, while the interface defect density increases to a maximum and subsequently decreases. The decrease in interface defect density leads to a recovery of surface passivation.

Microstructure Analysis of GaN Epitaxial Layers During Ion Implantation Using Synchrotron X-Ray Topography

Power electronic devices based on wide band-gap semiconductor materials such as GaN and SiC are rapidly being developed to replace traditional silicon-based devices whose performance has nearly reached their material limits. In the fabrication of GaN vertical power devices, selective area doping (SAD) processes are essential [1]. Several SAD techniques have been developed, including ion implantation [2], etching and regrowth method [3, 4], diffusion doping and neutron transmutation [5]. However, the influences of these procedures on the microstructures of GaN epitaxial layers is one of the key factors to determine the performance of the devices.In this study, ion-implanted GaN epitaxial layers from different stages including ammonothermal grown substrate material, metal organic chemical vapor deposition (MOCVD) epitaxial growth, ion implantation and subsequent annealing was characterized by synchrotron monochromatic beam X-ray topography (SMBXT) [6], synchrotron X-ray rocking curve topography (SXRCT) [7], and high-resolution X-ray diffraction (HRXRD). The change of distribution of threading dislocations (TDs) is characterized. The comparison of lattice strain of the material from each processing stage is conducted by both HRXRD and SXRCT.Enlarged contrast of screw and edge types of threading dislocations (TDs) on X-ray topographs after homoepitaxial growth is observed and likely due to interaction with point defects. X-ray topographs reveal ion implantation does not change the distribution of dislocations in the wafer. Strain and tilt maps derived from X-ray rocking curve topographs also show that annealing leads to an improvement in lattice bending levels. These results will be discussed with their implications for further processing into devices.

(Invited) Selective Area Etching and Doping of GaN for High-Power Applications

Selective-area doping techniques of GaN have been studied intensively for high-power applications. Diffusion or implantation of dopants is a very mature approach in Si and SiC, but it is still under investigation for GaN. Selective area epitaxy and doping is an alternative method to overcome the barrier and is reported by many groups. Two aspects will be discussed, including selective-area etching and non-uniform Mg doping in non-planar regrown trenches.Dry etching has been commonly applied to create high-aspect ratio and smooth trenches, but has also been reported to generate serious optical and electronic defects and impurities on the treated surface. Here, we report using an in-situ etchant, tertiarybutylchloride (TBCl), to replace the dry etching process. In order to demonstrate the effectiveness of TBCl etching, planar PN diodes were grown and fabricated, including continuous, dry-etched, and TBCl-etched and regrown ones. TBCl-etched and regrown device demonstrates electrical properties approach that of the continuous grown diode in the forward and reverse biased conditions.On the other hand, non-uniform doping of Mg was observed in the non-planar regrowth by several groups. With nanoscale characterization technique, atom probe tomography (APT), we identified the origin of the non-uniformity. The Mg concentration is approximately inversely proportional to the growth rate beginning ~20 nm from the regrowth interface. It indicates that the existence of semi-polar facets together with the anisotropy in the growth rate are the origin of non-uniformity. Furthermore, the evolving shape of semi-polar facets could be explained by the kinetic Wulff theorem.

(Invited) Understanding the Electroluminescence Signature of High-Voltage Vertical GaN Pin Diodes with Different Edge Termination Designs

GaN has superior properties, such as a wide band gap and high critical electric field that make it promising material for future power semiconductor devices. Edge termination for GaN power devices remains a subject of significant interest. In this work, different edge termination designs were systematically evaluated and compared by utilizing broadband electroluminescence technique under various reverse bias conditions. Edge termination is a crucial step in power devices fabrication process, using nitrogen implant is a common step in GaN PiN diode. In this work, Nitrogen ion implantation was used to form junction termination extension (JTE) and Guard Rings (GR). A full 2” wafer was fabricated in a foundry process to build a high current 1.2kV class GaN vertical diodes on non-homogenous GaN substrate. In silicon power devices, a smooth tapered implanted doping profiles are often achieved through a controlled diffusion of the implanted dopant island during activation. Activation and diffusion of acceptor dopants via ion implantation is neither well controlled nor understood in GaN. In this work, based JTE terminations, GR termination and a combination of both were compared. We are comparing several devices on the same wafer type and same fabrication process but with different edge termination designs; and spatially resolving their spectrum, by utilizing the electroluminescence mapping technique to acquire a series of broadband images under high voltage reverse bias. There is a clear difference in the electroluminescence signature. This is the first time we show the impact of edge termination on the evolution of these defects and the transport path of the leakage current. The leakage current, and hence the electroluminescence signature is changing as well with the termination design. All the termination and guard ring designs were based on Nitrogen implant. The nitrogen implant doses and energy are chosen to create enough damage in the p-type region. Stress testing is in-progress to evaluate the impact of these defects on failure mechanisms. JTE only design show a leakage current as a bright ring on the outer perimeter of the device active region closer to trench isolation while a GR only design brings the leakage current near the anode. A combination of both termination designs results in scattered leakage points on the outer perimeter of the device. Simulation results of the filed profiles of the different structures and hyperspectral EL and Raman spectroscopy are in progress along with temperature stressing to understand the nitrogen diffusion mechanisms in GaN. This study will have an impact on the future of GaN power devices and mature its process to compete with SiC technology. Figure 1

(Invited) Medium-Voltage SiC Devices for Next Generation of Power Conversion

As a wide bandgap semiconductor, Silicon Carbide (SiC) power switches and diodes offer the promise of lower conduction and switching losses and more efficient power conversion for a wide range of applications that include but not limited to hybrid vehicles, renewable technologies, industrial motors and data centers. However, in present day, SiC solutions for MV-class (>3.3 kV) unipolar switches and diodes suffer from high conduction losses at elevated temperatures, and SiC bipolar devices such as IGBTs require a prohibitive high forward voltage drop of 3V. Therefore, in these systems, the advantage of SiC technology is diminished compared to the incumbent Si IGBT technology. SiC super-junctions (SJ) can break the unipolar limit and offer an improved trade-off between specific on-resistance and blocking voltage for MV-class applications. To date, multi-epitaxial growth and trench-refill approaches have been demonstrated for 1.2kV and 6.5kV SiC SJ devices. Due to low diffusivity of dopants and shallow projectile depth of implanted atoms in SiC, multi-epitaxial solutions are limited to low voltage switches with thinner drift layers (up to 1200V). Alternately, the trench refill approach generates crystallographic defects that result in leakage at high blocking voltages. Furthermore, achieving uniform, target dopant distribution inside re-grown layers requires complex growth conditions and makes the regrowth process challenging. Recently, SiC charge-balanced (CB) diodes and MOSFETs were reported as an alternative solution to SJ devices with a simpler and scalable fabrication process. In these devices, a novel drift layer architecture is implemented with buried p-doped regions inside the drift layers instead of p-doped pillars. This new approach has been adopted for 3.3kV SiC JBS diodes and 4.5kV SiC MOSFET and results in Ron,sp significantly below the 1-D SiC unipolar limit. In the meantime, a new class of SJ devices is being developed that relies on Megavolt-level implantation to form deep p-type and n-type pillars. This multi-epitaxial SJ approach can be implemented in high voltage SiC devices with a smaller number of regrowth steps. In this work, we review fabrication steps for realizing SiC CB diodes and MOSFETs and report static characterization from room temperature up to 175 °C and dynamic response up to 3kV double pulse switching of such diodes and MOSFETs. Furthermore, we report successful fabrication of 2kV SiC SJ PiN diodes as a first building block of deep-implanted SJ technology and will discuss effect of different activation anneal temperatures on recovering lattice damage following high energy implantation.

Atomic-scale Dopant Integration During CMOS Device Fabrication

As CMOS device dimensions shrink and reach scaling limits, atomic layer-based processing has opened new routes for device fabrication and varied device physics. Atomic precision advanced manufacturing (APAM) for precise placement of dopants in Si either as individual atoms, scanning tunneling microscope (STM)-patterned lines, or as sheets of dopants (a delta layer) opens the opportunity to precisely engineer electronic structure and achieve doping above the traditional solubility limit [1]. APAM processing can complement traditional CMOS devices, modifying or augmenting chips including standard integrated circuits, and here we demonstrate a direct CMOS-integrated process flow for APAM processing.During APAM processing, a clean Si surface is exposed to vapor-phase dopant precursors such as phosphine which adsorb on exposed dangling Si bonds, followed by a thin Si cap. Traditionally, the surface preparation involves flash anneals near 1200 °C to achieve a clean, reconstructed Si surface as well as processing in ultrahigh vacuum for the doping and capping. Atomic-precision patterning is achieved with hydrogen termination then STM-based removal of H using the tip to reach pre-implanted contacts [2], though recent efforts have shown delta layer patterning without the STM using photothermal desorption of the H [3]. The high-temperature surface preparation is incompatible with CMOS process flows, but efforts to reduce the temperature have shown that temperatures of 800 °C or below may be sufficient to produce a clean Si surface [2,4].For direct integration of APAM structures in a CMOS flow, the middle-of-line processing near CMOS contact formation is a natural insertion point, when the device Si is accessible but the transistors’ high-temperature gate and dopant activation steps are finished. We estimate that APAM processing requires temperatures of 400-800 °C for surface preparation, but after APAM processing the devices should stay below about 600 °C to avoid dopant diffusion. By doing APAM processing before metal (copper or aluminum) deposition, the low 500-600 °C limit for MEMS-on-CMOS processing may be avoided [5].As a test platform, custom CMOS devices were fabricated in Sandia’s fab using the 0.35-micron node, including both discrete transistors and simple circuits such as gates and ring oscillators. Specialized cells in the layout enable the demonstration of APAM doping integrated with CMOS elements, with minimal changes to the CMOS flow and masks. After completing gate formation, the wafers are pulled near the contact module for UHV APAM processing, then finished with metallization in a separate fab to do electrical testing.Initial tests subjecting the CMOS chips to surface preparation techniques used for APAM processing show that the CMOS circuits can survive gentle flash anneals and sputter cleans, even when silicide and tungsten contacts are already in place. More in-depth rapid thermal anneal (RTA) studies of the chips’ thermal budget reveal degradation in drive currents and threshold voltages in n-channel devices starting about 600 °C, but switching operation is maintained through 800 °C where the tungsten contacts begin to severely degrade. Current work is ongoing to process samples without tungsten contacts already in place and to achieve delta layer doping on these chips. Our goal is to demonstrate atomic layer doping directly integrated with a CMOS process flow.In summary, atomic-precision device doping is integrated with a standard CMOS process flow, with the thermal budget of both the APAM and CMOS elements determining the fab requirements. If silicide and tungsten contacts are in place, the Si surface preparation techniques are limited to a temperature of about 600 °C which should be compatible with low-temperature options such as Ne sputtering and gentle anneals.SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.[1] B. Weber et al., Science 335, 64 (2012).[2] D. R. Ward et al., Appl. Phys. Lett. 111, 193101 (2017).[3] A. M. Katzenmeyer et al., J. Micro/Nanopattern. Mats. Metro. 20, 014901 (2021).[4] T. Skeren et al., Nanotechnology 29, 435302 (2018).[5] H. Takeuchi et al., IEEE Transactions on Electron Devices 52, 2081 (2005).

Improving the efficiency of an industrial silicon solar cell by doping with nickel

The possibility of adjusting the operational parameters of industrial solar cells produced by the company Suniva based on monocrystalline silicon by means of additional diffusion doping with nickel in the temperature range 700–1200 °C has been investigated. It is shown that the optimal temperature of nickel diffusion is Tdiff = 800–850 °C. In this case the value of the maximum power Pmax increases by 20–28 % in relation to the parameters of the original industrial photocell. At diffusion temperatures Tdiff > 1000 °C, a sharp decrease in Pmax occurs, which is associated with an increase in the depth of the p–n-junction due to the distillation of phosphorus atoms during high-temperature diffusion of nickel. The positive effect of diffusion alloying with nickel on the electrophysical parameters of photocells is greatest in the case when the nickel impurity clusters are in the region of the p–n-junction, i. e. with diffusion alloying to the front side of the plate. The action of electrically neutral nickel clusters is less pronounced when they are located in the region of the isotypic p–p+ transition; in case of diffusion alloying with nickel in the opposite side of the plate.

Strain mapping of silicon carbon suspended membranes

The alloy silicon carbon (Si1-yCy) has various strain engineering applications. It is often implemented as a dopant diffusion barrier and has been identified as a potential buffer layer for cubic silicon carbide (3C-SiC) heteroepitaxy. While suspended membranes formed from thin films of semiconductor (Ge and 3C-SiC) and dielectric (Si3N4) materials have been well studied, pseudomorphic, defect-free epilayers under high levels of tensile strain have received little attention. Often, tensile strain is a desired quality of semiconductors and enhancing this property can lead to various benefits of subsequent device applications. The strain state and crystalline tilt of suspended Si1-yCy epilayers have been investigated through micro-X-ray diffraction techniques. The in-plane tensile strain of the alloy was found to increase from 0.67% to 0.82%. This strain increase could reduce the C content required to achieve suitable levels of strain in such alloys and further strain enhancement could be externally induced. The source of this strain increase was found to stem from slight tilts at the edges of the membranes, however, the bulk of the suspended films remained flat. The novel process utilised to fabricate suspended Si1-yCy thin-films is applicable to many other materials that are typically not resistant to anisotropic Si wet etchants.