Performance Of Various Devices Research Articles

Swift heavy ion irradiation-driven energy band engineering and its profound influence on the photoresponse of β-Ga2O3 ultraviolet photodetectors

Swift heavy Ta ions with an ultra-high energy of 2896 MeV are utilized for irradiation of β-Ga2O3 photodetectors. Noteworthy variations in device performance under different wavelengths are observed. Under 254 nm light illumination, the photocurrent of the devices exhibit degradation at low ion fluences but gradually recover and even surpass the performance of non-irradiated devices at the irradiation fluence of 1 × 1010 cm−2. Conversely, under 365 nm light illumination, photocurrent increases at low fluence but slightly decreases at the same high fluence of 1 × 1010 cm−2. Cathodoluminescence spectra and first-principles calculations elucidate the mechanism underlying the evolution of device performance with irradiation fluence. At low irradiation fluence, the introduction of point defects such as oxygen vacancies and gallium vacancies leads to an expansion of the bandgap, resulting in a decline in photocurrent under 254 nm light illumination. Additionally, deep defect levels are generated by these point defects, promoting an enhancement of photocurrent under 365 nm light illumination. Higher fluences transform these point defects into complex defects such as Ga–O pair vacancies, resulting in a reduction in the bandgap. Consequently, an increase in photocurrent is observed for devices illuminated with 254 nm light. However, at high irradiation fluences, charge recombination induced by the presence of deep defect levels becomes more significant, leading to a decrease in photocurrent when exposed to 365 nm light. No matter what, at 1 × 1010 cm−2 fluence, β-Ga2O3 photodetectors still maintain excellent performance, implying their strong radiation resistance and immense potential for application in space environments.

Real-time monitoring polymerization degree of organic photovoltaic materials toward no batch-to-batch variations in device performance

Polymerization degree plays a vital role in material properties. Previous methodologies of molecular weight control generally cannot suppress or alleviate batch-to-batch variations in device performance, especially in polymer solar cells. Herein, we develop an in-situ photoluminescence system in tandem with a set of analysis and processing procedures to track and estimate the polymerization degree of organic photovoltaic materials. To support the development of this protocol, we introduce polymer acceptor PYT constructed by near-infrared Y-series small molecule acceptors via Stille polymerization, and shed light on the correlations between molecular weight, spectral parameters, and device efficiencies that enable the design of the optical setup and confirm its feasibility. The universality is verified in PYT derivatives with stereoregularity and fluoro-substitution as well as benzo[1,2-b:4,5-b’]dithiophene-based polymers. Overall, our result provides a tool to tailor suitable conjugated oligomers applied to polymer solar cells and other organic electronics for industrial scalability and desired cost reduction.

Decomposition of the anisotropic strain in 3D-structure GaN layers using Raman spectroscopy

Strain engineering for gallium nitride has been studied by many researchers to improve the performance of various devices (i.e., light-emitting diodes, laser diodes, power devices, high electron mobility transistors, and so on). Further miniaturization of gallium nitride devices will clearly continue in the future, and therefore an accurate understanding of the strain state in the devices is essential. However, a measurement technique for axially resolved evaluation of the strain in microareas has not yet been established. In this study, we revealed that the anisotropic strain state induced in c-plane growth gallium nitride is linked to the split state of Raman peaks, which were measured with z(xx)z¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$z(xx)\\overline{z }$$\\end{document} and z(yx)z¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$z(yx)\\overline{z }$$\\end{document} polarized configurations. The anisotropic strain state in c-plane gallium nitride was induced in the 3D-structure by epitaxial lateral overgrowth, which enabled successful performance of our work. This result allowed us to axially decompose the strain in c-plane gallium nitride through Raman spectroscopy and establish a measurement technique for axially resolving the strain. This measurement technique is feasible using a conventional Raman spectrometer. Furthermore, the method was indicated to be applicable to all wurtzite-type crystals, including gallium nitride, silicon carbide, and aluminum nitride. Our work provides a new perspective for understanding the complex strain state in microareas for wurtzite materials. Comprehending the strain state, which strongly affects device performance, will help promote the research and development of III-V semiconductor devices.

Polymer-Doped SnO2 as an Electron Transport Layer for Highly Efficient and Stable Perovskite Solar Cells.

To produce highly efficient and repeatable perovskite solar cells (PSCs), comprehending interfacial loss and developing approaches to ameliorate interfacial features is essential. Nonradiative recombination at the SnO2-perovskite interface in SnO2-based perovskite solar cells (PSCs) leads to significant potential loss and variability in device performance. To improve the quality of the SnO2 electron transport layer, a novel polymer-doped SnO2 matrix, specifically using polyacrylic acid, was developed. This matrix is formed by spin-coating a SnO2 colloidal solution that includes polymers. The polymer aids in dispersing nanoparticles within the substrate and is evenly distributed in the SnO2 solution. As a result of the polymer addition, the density and wetting properties of the SnO2 layer substantially improved. Subsequently, perovskite-based photovoltaic devices comprising SnO2 and Spiro-OMeTAD layers and using (FAPbI3)0.97(MAPbBr3)0.03 perovskite are constructed. These optimized devices exhibited an increased efficiency of 17.2% when compared to the 15.7% power conversion efficiency of the control device. The incorporation of polymers in the electron transport layer potentially enables even better performance in planar perovskite solar cells.

Delivering biochemicals with precision using bioelectronic devices enhanced with feedback control.

Precision medicine endeavors to personalize treatments, considering individual variations in patient responses based on factors like genetic mutations, age, and diet. Integrating this approach dynamically, bioelectronics equipped with real-time sensing and intelligent actuation present a promising avenue. Devices such as ion pumps hold potential for precise therapeutic drug delivery, a pivotal aspect of effective precision medicine. However, implementing bioelectronic devices in precision medicine encounters formidable challenges. Variability in device performance due to fabrication inconsistencies and operational limitations, including voltage saturation, presents significant hurdles. To address this, closed-loop control with adaptive capabilities and explicit handling of saturation becomes imperative. Our research introduces an enhanced sliding mode controller capable of managing saturation, adept at satisfactory control actions amidst model uncertainties. To evaluate the controller's effectiveness, we conducted in silico experiments using an extended mathematical model of the proton pump. Subsequently, we compared the performance of our developed controller with classical Proportional Integral Derivative (PID) and machine learning (ML)-based controllers. Furthermore, in vitro experiments assessed the controller's efficacy using various reference signals for controlled Fluoxetine delivery. These experiments showcased consistent performance across diverse input signals, maintaining the current value near the reference with a relative error of less than 7% in all trials. Our findings underscore the potential of the developed controller to address challenges in bioelectronic device implementation, offering reliable precision in drug delivery strategies within the realm of precision medicine.

Comparative structure, optical and electrical characteristics of sol-gel-deposited In-, Ga-, and Sn-doped CuO thin films

Doping of metal-oxide thin films provides an effective method to improve the performance of various devices based on them such as solar cells, photodetectors, and gas sensors. Developing high-performance of these devices, the influence of In, Ga, and Sn dopants on structure, optical and electrical characteristics of CuO deserves further study. Herein, undoped and In-, Ga-, and Sn-doped CuO thin films are deposited on glass substrates by the sol-gel method, and the parameters influenced by these dopants are determined systematically. The effect of studied dopants on XRD, SEM, UV-vis, PL, and electrical conductivity measurements are examined, and the results are correlated with each other. Additionally, the electrical transport mechanism of the films is comprehensively investigated. It is determined that the multi-phonon hopping (MPH) conduction mechanism governs the temperature-dependent conductivity of the films. Finally, it is found that the probed dopants significantly impact the properties of CuO thin film.

Exploring the influence of external electric fields on the mechanical characteristics of zirconium disulfide nanosheets via density functional theory

The density functional theory is utilized to investigate elastic and plastic properties of zirconium disulfide (ZrS2) nanosheet subjected to a uniform external electric field up to 4 VÅ. In this respect, firstly, unit cell dimensions, bond lengths and bond angles are obtained by optimizing the unit cell of ZrS2nanosheet, and the most stable configuration is considered for the nanostructure accordingly. Then, by applying uniaxial and biaxial tensions on the nanosheet under a uniform external electric field, Young's and bulk moduli are computed, respectively. Finally, the applied strain is extended to the plastic region to evaluate the effect of external electric field on the first and second critical strains. It is shown that applying external electric field results in increasing Young's modulus of the nanosheet. However, the bulk modulus increases up to 2 VÅ and deceases afterwards. Besides, the first and second critical strains, which are respectively used to show the end of harmonic and inharmonic regions, decrease in the presence of the external electric field while the difference between them is not affected by the external electric field. Investigating the elastic and plastic properties of zirconium disulfide under an external electric field is important for both fundamental research and practical applications. It can help us develop new materials with tunable properties, optimize their performance in various devices, and contribute to the development of cutting-edge technologies

Reliability study of nano ribbon FET with temperature variation including interface trap charges

The nano ribbon FET (NR-FET) is an emerging device as multigate structure can be designed on a single substrate, which leads to improvement in device performance. However, the presence of multiple gate oxide and semiconductor interface creates a number of interface trap charges (ITCs), which leads to variation in device performance. In this paper, the assessment of reliability for NR-FET is performed under the impact of ITCs for different polarity. We have incorporated the ITCs along with wide variations in temperature from 200 to 500 K to study the DC, RF/analog, and linearity performance of NR-FET. It is seen that the increase in amount of positive ITCs (PITCs) leads to improvement in ON state current and less gate voltage is required to turn on the device. Also, the cut-off frequency and speed of the device can be improved through increasing the PITCs in NR-FET. The degradation in OFF state current and device efficiency (gm/ID) is observed with increased in temperature from 200 to 500 K. However, the linearity characteristics is improved at high temperature for different polarity in ITCs. This device provides ION = 9.77 × 10−4 A, IOFF = 6.23 × 10−13 A, maximum transconductance of 1.4 mS, maximum transconductance generation factor of 36.56 V−1, maximum cut-off frequency of 4.36 × 1012 Hz, delay of 39.6 ps, threshold voltage of 0.4301 V at trap level concentration of 1012 Ccm−2. It is also seen that NR-FET outperforms in terms of DC and RF/analog characteristics with the variation in temperature from 200 to 500 K. The temperature sensitivity is 150 (80) under PITC (NITC) for this NRFET. Due to its improved behaviour in wide range of temperature 200–500 K, this NR-FET can be applicable for defense and space applications.

Compact Modeling of Process Variations in Nanosheet Complementary FET (CFET) and Circuit Performance Predictions

In this work, a semi-analytical compact model of random process fluctuations in nanosheet (NS) gate-all-around (GAA) complementary FET (CFET) is proposed, including work-function variation (WFV), line edge roughness (LER), and gate edge roughness (GER). Different from the conventional NS GAA FET, GER has a significantly different impact on NS GAA CFET, due to the additional p-type work-function (p-WF) liner for p-FET threshold voltage tuning as well as the common metal gate, and a negative correlation with p-WF thickness is introduced into GER model. The proposed model is embedded into Berkeley short-channel insulated-gate field-effect transistor model-common multi-gate (BSIM-CMG) to predict the device performance variability by HSPICE Monte Carlo (MC) simulations. Excellent agreement between stochastic TCAD and HSPICE MC simulations is demonstrated. The effect of process variations on the power-performance-area (PPA) of standard cells (SDCs) and ring oscillator (RO) circuit is predicted by the proposed model. Most of the process variations make a more than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 10% to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$+$</tex-math> </inline-formula> 20% change in power consumption in NOR2. WFV has the greatest impact on RO PPA, making a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 10% to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$+$</tex-math> </inline-formula> 12.3% change in power consumption. The proposed model provides a helpful guideline for the random variation-aware CFET circuit design and related technology process development.

Investigating the Device Performance Variation of a Buried Locally Gated Al/Al2O3 Graphene Field-Effect Transistor Process

In this study, a process is developed for the fabrication of buried top-gated graphene transistors with Al2O3 as a gate dielectric, yielding devices that can be suitable for not only flexible electronics but also laser-induced graphene (LIG)-based technology implementations. A new processing option is presented with the use of tetraethyl-orthosilicate (TEOS) as an etch stop for contact via etching of Al2O3. Buried locally gated Al/Al2O3 graphene field-effect transistors (GFETs) are fabricated with Dirac points as low as 4 V, with a metal-to-graphene contact resistance as low as ∼1.7 kΩ·µm, and an average hole mobility of 457.97 cm2/V·s with a non-uniformity of 93%. Large device variation and non-uniformity in electrical performance are not uncommon for graphene-based devices, as process-induced defects play a major role in such variation. AFM, SEM, Raman spectroscopy, and model fitting indicated that the rough Al/Al2O3 surface was the main factor for the observed device variation. AFM analysis indicated a graphene surface roughness Ra of 16.19 nm on top of the buried Al/Al2O3 gate in contrast to a Ra of 4.06 nm over Al2O3/SiO2. The results presented indicate the need to reduce device variability and non-uniformity by improving transfer methods, as well as the use of smoother surfaces and compatible materials. The presented analyses provide a framework with which other researchers can analyze and correlate device variation and non-uniformities while methods to reduce variability are investigated.

Optimization of ITO/SnO2/FASnI3/PCBM/Ag based perovskite solar cell

In the present work, a numerical simulation of perovskite solar cell: ITO/SnO2/FASnI3/PCBM/Ag is carried out by using one dimensional simulation software i.e., SCAPS-1D. The variation of device performance with absorber thickness is evaluated. Solar cells cannot be made entirely from pure materials. Impurities that serve as trapping centres must be present. A detailed study is conducted to analyse the impact of absorber defect density on performance parameters, and the results indicate that as defects rise, device performance decreases. The cell performance is influenced by the operating temperature. The best power conversion efficiency after optimization is 24.54% (Voc = 0.97 V, Jsc = 29.88 mA/cm2 and FF = 84.39. The current investigation shows a considerable possibility for producing a lead-free device with good efficiency.

Toward More Efficient Organic Solar Cells: A Detailed Study of Loss Pathway and Its Impact on Overall Device Performance in Low‐Offset Organic Solar Cells

AbstractLow‐offset organic solar cell systems have attracted great interest since nonfullerene acceptors came into the picture. While numerous studies have focused on the charge generation process in these low‐offset systems, only a few studies have focused on the details of each loss channel in the charge generation process and their impact on the overall device performance. Here, several nonfullerene acceptors are blended with the same polymer donor to form a series of low‐offset organic solar cell systems where significant variation in device performance is observed. Through detailed analyses of loss pathways, it is found that: i) the donor:acceptor interfaces of PM6:Y6 and PM6:TPT10 are close to the optimum energetic condition, ii) energetics at the donor:acceptor interface are the most important factor to the overall device performance, iii) exciton dissociation yield can be field‐dependent owing to the sufficiently small energetic offset at the donor:acceptor interface, and iv) the change in substituents in the terminal group of Y‐series acceptors in this work mainly affects energetics at the donor:acceptor interface instead of the interface density in the active layer. In general, this work presents a path toward more efficient organic solar cells.

Regulating Radial Morphology in Hot-Casting Two-Dimensional Ruddlesden–Popper Perovskite Film Growth for High-Efficient Photovoltaics

Two-dimensional (2D) perovskites have attracted significant attention in recent years due to their promising light harvesting and emissive properties. However, the realization of 2D perovskite crystallization with sufficient coverage and reliable reproducibility remains difficult. In this study, controlling the solvent volatilization to achieve high-quality crystallization with full coverage and lateral homogeneity of 2D Ruddlesden–Popper phase perovskite was effectively achieved. It is found that variations in the solvent evaporation rate give rise to lateral film coverage gradients with the degree of grain fusion during the process of hot-casting. As a result, the obtained photovoltaic efficiency varies due to the growth inhomogeneity across hot-casting thin films from center to edge. By adjusting the temperature of the casting perovskite precursor, film inhomogeneity and device performance variation can be alleviated. Regulating radial morphology across hot-casting thin films will enable coating techniques amenable to the solution process for robust reproducibility.

Interface layer modulation of an all-inorganic perovskite solar cell to study the carrier transport mechanism

Over the past decade, organic halide perovskite has been an excellent absorber in solar cells. However, their stability issues have forced the research community to search for purely inorganic perovskites. In this work, we designed a perovskite solar cell based on a purely inorganic Cs0.8Rb0.2SnI3 absorber layer with inorganic carrier transport layers using SCAPS-1D simulation software. Using this exemplary architecture, we have discussed different carrier movement mechanisms in the conduction and valence bands through the interfaces of the absorber and carrier transport layers by instigating two interface layers. Our results illustrate the variation in device performance with the electron affinities and diffusion lengths. In addition, the study demonstrates a positive impact of Rb doping in CsSnI3 based perovskite solar cells. The absorber thickness and defect density optimization are also executed to maximize the solar cell performance. The optimized electron affinities of the interface layers are found to be 4.1 and 4.3 eV, respectively. The final model of the device has achieved a photo-conversion efficiency of 23% with a short circuit current of about 30 mA cm−2. The optimized model covers the entire visible solar spectrum with a quantum efficiency of >90%.

Process Development of Amorphous Indium Tin Gallium Oxide (ITGO) Thin Film Transistors

The invention of portable electronic devices had a huge impact on the growing interest in flat panel displays. Since the first report in 2004 on amorphous Indium Gallium Zinc Oxide (a-IGZO) thin film transistors (TFTs), many companies have become interested in this material. The main advantage of a-IGZO over conventional amorphous silicon TFTs is its steep subthreshold, low off state current, and high channel mobility. However, the demand for larger displays with higher resolution and refresh rates is driving the demand for TFTs with higher performance, while avoiding the cost and complexity associated with low temperature polycrystalline silicon. There is an increased focus on alternative amorphous oxide semiconductors for use as TFT channel materials, due to the success of a-IGZO.The focus of this study is an investigation on Indium-Tin-Gallium-Oxide (ITGO) TFTs. Unpassivated bottom-gate devices were fabricated with a 30nm a-ITGO film, sputter deposited with 1% and 10% oxygen gas ambient, followed by a 2 hour anneal at 300oC in oxygen. Devices fabricated with PO2 = 1% resulted in a highly conductive channel. Devices with PO2 = 10% displayed semiconducting behavior and a shallow subthreshold. This trend held for all device dimensions tested; lengths of 24µm, 12µm, and 6µm with a width of 24µm. Compared to a-IGZO devices with a length of 4µm, ITGO devices with a length of 12µm exhibit an equivalent current drive, implying a 3 to 4 times improvement in mobility.Following aging in room ambient for multiple days, a-ITGO devices displayed improved yet left-shifted transfer characteristics. In unpassivated a-IGZO devices, similar behavior can also be observed and is attributed to an inhomogeneous trap distribution across the channel. As the exposed channel reacts with room air, oxygen vacancies are filled resulting in a more homogeneous trap distribution. A radial variation of device performance from the center of the wafer to the edge was also observed. When measuring devices towards the edge of the wafer a considerable left shift in transfer characteristics was observed. This variation in device performance is believed to be attributed to non-uniformities in the as deposited ITGO film and will be related to material optical parameters. Figure 1

(Invited) Biomimetic Eyes with Perovskite Nanowire Array Retina

Human eyes are masterpiece of nature, which can realize powerful image sensing with a very concise structure. Biomimetic eyes with characters comparable to human eyes are highly desirable in many technological applications, particularly in the fields of visual prosthesis and machine vision. The World Health Organization reported that globally there are over 252 million people suffering from visual impairment in the year of 2020. This number is exploding due to the prevalence of various mobile devices with small displays. Bionic eyes implantation is one the most effective strategy for vison restoration. However, today, even the most mature bionic eyes have only 300 clinical trials, which is merely 1 ppm of all the visual impaired patients, mainly due to their poor performance and high cost. In addition, industrial applications such as autonomous driving and humanoids also desire cameras with high performance. To achieve biomimetic eyes with imaging performance on a par with human eyes, innovative device structure design and material selection have to be carried out simultaneously. Among all the photosensing material candidates, the ordered one-dimensional (1D) semiconductor nanowire (NW) arrays exhibit unique advantages such as fast carrier transportation and strong light-material interaction due to their anisotropic structure in axial and radial direction, thereby leading to fast response and high responsivity. This presentation focuses on our work on the NW arrays image sensing and can be highlighted as:1) Controlled growth of well aligned, high-density NW arraysDespite the advantages abovementioned, the integration of NWs has always been a bottleneck challenge hurdling their practical applications. Direct growth of NW arrays can be an effective way to tackle this challenge. We reported for the first time a unique fabrication process to form large-scale, 3D, high-density arrays of lead halide perovskite NWs with well-engineered geometry through a template-assisted growth approach. The array demonstrated amazingly geometry dependent optoelectronic properties and thereby can be used to improve performance of various devices. Particularly, its high regularity leads to the possibility to electrically addressable individual NWs which makes it an ideal candidate for very-large-scale integrated (VLSI) electronics and optoelectronics. The interaction between nanotemplate and sensing materials can introduce unique device performance such as tunable photoresponse and improved stability of perovskites.2) Assembly of integrated, NW arrays based planar image sensorsTo demonstrate the technological potency of the NW arrays, we have developed new process to fabricate them into proof-of-concept image sensors. Each image sensor consists of 1,024 photodiode pixels made of vertical perovskite NWs, and the imaging functionality has been verified by recognizing various optical patterns projected onto it. The high density of this NW array and the addressability of individual NW enable this unique image sensor design a potential, extremely high resolution approaching optical diffraction limit. To realize the device assembly, we have developed a PDMS-assisted dry transfer process which can transfer the thin (µm scale) and large-area (cm scale) film onto any substrate without any bubbles and wrinkles. This unique NW manipulation strategy, together with NW geometrical and compositional tunability, may lead to new functionality and inspire novel device design in the future.3) Invention of a 3D, biomimetic eye with a hemispherical NW array retinaThe high performance of human eyes originates from the dome shape of retina and the high-density photoreceptors in it. However, the commercial image sensors are dominantly using planar device structures shaped by the mainstream planar microfabrication processes, making it hardly possible for hemispherical device fabrication. In our work, we have developed a novel artificial visual system using a spherical biomimetic electrochemical eye with hemispherical retina made of a high-density perovskite NW array. The device has high similarity to human eyes with part of its photodetection performance superior to human eyes. The hemispherical artificial retina has NW density much higher than that of photoreceptors in a human retina thus can potentially achieve a higher image resolution which is bolstered by implementation of a single-NW ultra-small photodetector. The work may lead to a new generation of photosensing devices based on a bioinspired design that can benefit a wide spectrum of technological applications.In all, with the unique structural properties of NW arrays as the starting point, we realized their controlled growth, developed strategies to manipulate them and designed proper device structures to fully fulfill their advantages. In the future, we will combine them with brains, either biological or digital brains, to explore their applications in fields such as visual prothesis and artificial intelligence. Figure 1

Process Development of Amorphous Indium Tin Gallium Oxide (ITGO) Thin Film Transistors

The focus of this study is an investigation on Indium-Tin-Gallium-Oxide (ITGO) TFTs. Unpassivated bottom-gate devices werefabricated with a sputter-deposited 30nm a-ITGO film with 1% and10% oxygen gas ambient, followed by a 1 or 2 hour anneal at 300oCin oxygen. Devices fabricated with PO2 = 1% resulted in a highlyconductive channel, whereas devices with PO2 = 10% displayedsemiconducting behavior and a shallow subthreshold. Followingaging in room ambient for multiple days, devices displayed left-shifted transfer characteristics with steep subthreshold. It ishypothesized that the unpassivated back-channel attains a morehomogeneous trap distribution. The ITGO devices demonstrate aneffective channel mobility approximately 2.5 times higher thanIGZO TFTs. Radial variation in device performance can beattributed to non-uniformities in the as-deposited ITGO film, with acorrelation to the distribution in optical constants across the wafer.

Integrated biosensor platform based on graphene transistor arrays for real-time high-accuracy ion sensing

Two-dimensional materials such as graphene have shown great promise as biosensors, but suffer from large device-to-device variation due to non-uniform material synthesis and device fabrication technologies. Here, we develop a robust bioelectronic sensing platform composed of more than 200 integrated sensing units, custom-built high-speed readout electronics, and machine learning inference that overcomes these challenges to achieve rapid, portable, and reliable measurements. The platform demonstrates reconfigurable multi-ion electrolyte sensing capability and provides highly sensitive, reversible, and real-time response for potassium, sodium, and calcium ions in complex solutions despite variations in device performance. A calibration method leveraging the sensor redundancy and device-to-device variation is also proposed, while a machine learning model trained with multi-dimensional information collected through the multiplexed sensor array is used to enhance the sensing system’s functionality and accuracy in ion classification.

Enhanced performance of p-type SnO x thin film transistors through defect compensation

Due to the unique outermost orbitals of Sn, hole carriers in tin monoxide (SnO) possess small effective mass and high mobility among oxide semiconductors, making it a promising p-channel material for thin film field-effect transistors (TFTs). However, the Sn vacancy induced field-effect mobility deterioration and threshold voltage (V th) shift in experiments greatly limit its application in complementary metal-oxide-semiconductor (CMOS) transistors. In this study, the internal mechanism of vacancy defect compensation by aluminum (Al) doping in SnO x film is studied combining experiments with the density functional theory (DFT). The doping is achieved by an argon (Ar) plasma treatment of Al2O3 deposited onto the SnO x film, in which the Al2O3 provides both the surface passivation and Al doping source. Experimental results show a wide V th modulation range (6.08 to −19.77 V) and notable mobility enhancement (11.56 cm2V−1s−1) in the SnO x TFTs after the Al doping by Ar plasma. DFT results reveal that the most possible positions of Al in SnO and SnO2 segments are the compensation to Sn vacancy and interstitial. The compensation will create an n-type doping effect and improve the hole carrier transport by reducing the hole effective mass (m h*), which is responsible for the device performance variation, while the interstitial in the SnO2 segment can hardly affect the valence transport of the film. The defect compensation is suitable for the electronic property modulation of SnO towards the high-performance CMOS application.

Te/CdTe and Al/CdTe Interfacial Energy Band Alignment by Atomistic Modeling.

A synergistic approach that incorporates first-principles atomistic modeling with numerical device simulations is used to systematically evaluate the role of heterointerfaces within metal-chalcogenide-based photovoltaic technologies. Two interfaces involving either a tellurium back contact or aluminum back electrode combined with a cadmium telluride absorber layer within cadmium-telluride-based thin-film solar cells are investigated on an atomic scale to determine the mechanisms contributing to variations in device performance. Electronic structures and predicted charge transport behavior with respect to cadmium and tellurium termination of the absorber layer are studied along the polar oriented CdTe{111} facets. The computational methodology reveals a noticeable contrast between the Schottky barrier forming Al/CdTe interface versus the Type I Te/CdTe heterojunction. Greater band bending features are exhibited by the cadmium termination as opposed to the tellurium termination for each interface case. Subsequent device modeling suggests that 3.6% higher photovoltaic conversion efficiency is achievable for the cadmium termination relative to the tellurium termination of the Te/CdTe interface. Based strictly on an idealistic representation, both interface models show the importance of atomic-scale interfacial properties for cadmium telluride solar cell device performance with their bulk properties being validated in comparison to published experimental data. The synergistic approach offers a suitable method to analyze solar cell interfaces through a predictive computational framework for the engineering and optimization of metal-chalcogenide-based thin-film photovoltaic technologies.