Performance Of Various Devices Research Articles

Comparative evaluation of the accuracy of electronic apex locators and cone-beam computed tomography in detection of root canal perforation and working length during endodontic retreatment

BackgroundTo evaluate the accuracy of the electronic apex locators (EALs), and Cone-Beam Computed Tomography (CBCT) scanning, both in working length (WL) determination and in the detection of root canal perforations in retreatment cases.MethodsSixty human mandibular premolars were selected. After crown removal partially and canal access, root canals were instrumented and irrigated. The obturation process utilized gutta-percha and sealer with warm vertical compaction. Two groups were distinguished: one without perforation (Group 1) and the other with an apical third perforation (Group 2). Retreatment included filling removal, apical preparation, and irrigation. Actual working lengths (AWL) were determined using a stereomicroscope. CBCT images were used to measure CBCT working length (CWL), with adjustments for optimal views. Propex II and Dentaport ZX were used to measure electronic working length (EWL). Differences between EWL and AWL, as well as CWL, were analyzed to gauge accuracy. Data underwent Two-way ANOVA analysis. Measurements within ± 0.5 and ± 1 mm tolerance ranges were deemed successful for each device, followed by applying the Pearson Chi-square test.ResultsThe study reveals no significant inter-group variations in device performance (p > .05). Dentaport ZX missed detecting perforation in two Group 2 (apical perforation) cases. For ± 1 mm tolerance, Propex II displayed the highest success in Group 2 (apical perforation).ConclusionThis study demonstrates the comparable performance of Propex II, Dentaport ZX, and CBCT in endodontic retreatment, providing insights into diagnostic reliability.

Interband cascade light-emitting diodes grown on silicon substrates using GaSb buffer layer

Interband cascade light-emitting diodes (ICLEDs) offer attractive advantages for infrared applications, which would greatly expand if high-quality growth on silicon substrates could be achieved. This work describes the formation of threading dislocations in ICLEDs grown monolithically on GaSb-on-Silicon wafers. The epitaxial growth is done in two stages: the GaSb-on-Silicon buffer is grown first, followed by the ICLED growth. The buffer growth involves the nucleation of a 10-nm-thick AlSb buffer layer on the silicon surface, followed by the GaSb growth. The AlSb nucleation layer promotes the formation of 90° and 60° interfacial misfit dislocations, resulting in a highly planar morphology for subsequent GaSb growth that is almost 100% relaxed. The resulting GaSb buffer for growth of the ICLED has a threading dislocation density of ∼107/cm2 after ∼3 μm of growth. The fabricated LEDs showed variations in device performance, with some devices demonstrating comparable light–current–voltage curves to those for devices grown on GaSb substrates, while other devices showed somewhat reduced relative performance. Cross-sectional transmission electron microscopy observations of the inferior diodes indicated that the multiplication of threading dislocations in the active region had most likely caused the increased leakage current and lower output power. Enhanced defect filter layers on the GaSb/Si substrates should provide more consistent diode performance and a viable future growth approach for antimonide-based ICLEDs and other infrared devices.

Metamaterial terahertz device with temperature regulation function that can achieve perfect absorption and complete reflection conversion of ultrawideband

The field of terahertz devices is important in terahertz technology. However, most of the current devices have limited functionality and poor performance. To improve device performance and achieve multifunctionality, we designed a terahertz device based on a combination of VO2 and metamaterials. This device can be tuned using the phase-transition characteristics of VO2, which is included in the triple-layer structure of the device, along with SiO2 and Au. The terahertz device exhibits various advantageous features, including broadband coverage, high absorption capability, dynamic tunability, simple structural design, polarization insensitivity, and incident-angle insensitivity. The simulation results showed that by controlling the temperature, the terahertz device achieved a thermal modulation range of spectral absorption from 0 to 0.99. At 313 K, the device exhibited complete reflection of terahertz waves. As the temperature increased, the absorption rate also increased. When the temperature reached 353 K, the device absorption rate exceeded 97.7% in the range of 5–8.55 THz. This study used the effective medium theory to elucidate the correlation between conductivity and temperature during the phase transition of VO2. Simultaneously, the variation in device performance was further elucidated by analyzing and depicting the intensity distribution of the electric field on the device surface at different temperatures. Furthermore, the impact of various structural parameters on device performance was examined, offering valuable insights and suggestions for selecting suitable parameter values in real-world applications. These characteristics render the device highly promising for applications in stealth technology, energy harvesting, modulation, and other related fields, thus showcasing its significant potential.

Comparison of performance in GaN-HEMTs on thin SiC substrate and sapphire substrates

We have investigated the electrical properties of GaN-based high electron mobility transistors (HEMT) on N+-type 4H SiC substrates and on sapphire substrate as a reference. The three-terminal off-state breakdown voltage (BV) as a function of gate-drain spacing (LGD) was measured. Both devices possess superior Baliga figure of merit parameters (BFOM= BV3/Ron). For GaN/Sapphire with LGD of 10 μm, Ron is 14.65 mΩ·cm2 and the corresponding BFOM yields a remarkably high value of 9.88 × 108V2·Ω−1·cm−2. Conversely, GaN/N+ SiC with 20 μm LGD exhibited an Ron of 43.23 mΩ·cm2 and a BFOM value of 1.55 × 107V2·Ω−1·cm−2. In addition, we perform AFM, XRD, SEM and TEM analysis to further explore the differences in the DC-current properties for these two distinct substrates. The XRD FWHM scales with surface roughness, moreover grain boundaries for GaN-based HEMTs grown on SiC are more distinct compared to Sapphire substrate. This study provide valuable insight into the structural and morphological disparities that may contribute to the observed variations in device performance.

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.

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.

A novel single ended 3T SRAM cell using FinFET technology for low power applications

The conventional planar Metal-Oxide-Semiconductor FETs (MOSFETs) are being replaced with Fin Field-Effect Transistors (FinFETs) due to their improved ability to manage power dissipation, propagation delay, leakage current, and short channel effects. Process variability is an issue for planar MOSFETs, however the amount of dopant ions in FinFETs reduces device performance variability. In this study, a Static-Random Access Memory (SRAM) cell employing FinFET technology is designed using three MOS transistors. It is composed of two NMOS plus a single PMOS transistor. One NMOS acts as access transistor while the pull-up and pull-down functions are performed by remaining NMOS and PMOS transistors, respectively. The proposed SRAM cell is simulated using H-SPICE simulator and is compared with existing SRAM cell designs in terms delay, power consumption and transistor count. Performance analysis shows that the proposed SRAM Cell overcomes the constraint and achieves full swing storage of logic values between 0 and 1. This justifies the definition of static. Implementing a single-ended SRAM cell also has the benefit of simplifying the SRAM cell architecture, which also results in a reduction in area.

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