Analysis of Channel Current Noise in Small Nanoscale Metal Oxide Semiconductor Field Effect Transistors.

The shrinkage of metal oxide semiconductor field effect transistor (MOSFET) to the small size of the nanoscale results in changes in their channel current noise composition. This paper determines the channel current noise composition of 90 nm MOSFET through experiments, and according to the device material and noise characteristics analysis, the channel current noise of 90 nm and below is obtained, which not only contains thermal noise and suppressed channel shot noise, but also adds suppressed gate tunneling shot noise and cross-correlation noise. Then, Monte Carlo simulation of 10 nm MOSFET noise is further used to determine the channel current composition of small size nanoscale devices. Subsequently, based on the device structure and fundamental characteristics of channel current noise, the channel current noise model is established. Finally, this model is employed to analyze the relationship between thermal noise, suppressed shot noise, cross-correlation noise, and channel current noise in relation to bias parameters and device characteristics. The theoretical results are basically consistent with the experimental and the simulated results, and the channel noise increases with the increase of bias voltage. This achievement holds promise for enhancing the operational efficiency, reliability, and lifetime of nanoscale small-sized MOSFET devices.

Three-micrometer-diameter needle electrode with an amplifier for extracellular in vivo recordings.

Microscale needle-electrode devices offer neuronal signal recording capability in brain tissue; however, using needles of smaller geometry to minimize tissue damage causes degradation of electrical properties, including high electrical impedance and low signal-to-noise ratio (SNR) recording. We overcome these limitations using a device assembly technique that uses a single needle-topped amplifier package, called STACK, within a device of ∼1 × 1 mm2 Based on silicon (Si) growth technology, a <3-µm-tip-diameter, 400-µm-length needle electrode was fabricated on a Si block as the module. The high electrical impedance characteristics of the needle electrode were improved by stacking it on the other module of the amplifier. The STACK device exhibited a voltage gain of >0.98 (-0.175 dB), enabling recording of the local field potential and action potentials from the mouse brain in vivo with an improved SNR of 6.2. Additionally, the device allowed us to use a Bluetooth module to demonstrate wireless recording of these neuronal signals; the chronic experiment was also conducted using STACK-implanted mice.

Gas Sensing Properties of Indium-Oxide-Based Field-Effect Transistor: A Review.

Excellent stability, low cost, high response, and sensitivity of indium oxide (In2O3), a metal oxide semiconductor, have been verified in the field of gas sensing. Conventional In2O3 gas sensors employ simple and easy-to-manufacture resistive components as transducers. However, the swift advancement of the Internet of Things has raised higher requirements for gas sensors based on metal oxides, primarily including lowering operating temperatures, improving selectivity, and realizing integrability. In response to these three main concerns, field-effect transistor (FET) gas sensors have garnered growing interest over the past decade. When compared with other metal oxide semiconductors, In2O3 exhibits greater carrier concentration and mobility. The property is advantageous for manufacturing FETs with exceptional electrical performance, provided that the off-state current is controlled at a sufficiently low level. This review presents the significant progress made in In2O3 FET gas sensors during the last ten years, covering typical device designs, gas sensing performance indicators, optimization techniques, and strategies for the future development based on In2O3 FET gas sensors.

Impact of Channel Thickness and Doping Concentration for Normally-Off Operation in Sn-Doped ß-Ga2O3 Phototransistors.

We demonstrate a Sn-doped monoclinic gallium oxide (ß-Ga2O3)-based deep ultraviolet (DUV) phototransistor with high area coverage and manufacturing efficiency. The threshold voltage (VT) switches between negative and positive depending on the ß-Ga2O3 channel thickness and doping concentration. Channel depletion and Ga diffusion during manufacturing significantly influence device characteristics, as validated through computer-aided design (TCAD) simulations, which agree with the experimental results. We achieved enhancement-mode (e-mode) operation in <10 nm-thick channels, enabling a zero VG to achieve a low dark current (1.84 pA) in a fully depleted equilibrium. Quantum confinement in thin ß-Ga2O3 layers enhances UV detection (down to 210 nm) by widening the band gap. Compared with bulk materials, dimensionally constrained optical absorption reduces electron-phonon interactions and phonon scattering, leading to faster optical responses. Decreasing ß-Ga2O3 channel thickness reduces VT and VG, enhancing power efficiency, dark current, and the photo-to-dark current ratio under dark and illuminated conditions. These results can guide the fabrication of tailored Ga2O3-based DUV phototransistors.

Low temperature passivation of silicon surfaces for enhanced performance of Schottky-barrier MOSFET.

By using a simple device architecture along with a simple process design and a low thermal-budget of a maximum of 100 °C for passivating metal/semiconductor interfaces, a Schottky barrier MOSFET device with a low subthreshold slope of 70 mV dec-1could be developed. This device is enabled after passivation of the metal/silicon interface (found at the source/drain regions) with ultra-thin SiOxfilms, followed by the e-beam evaporation of high- quality aluminum and by using atomic-layer deposition for HfO2as a gate oxide. All of these fabrication steps were designed in a sequential process so that a gate-last recipe could minimize the defect density at the aluminum/silicon and HfO2/silicon interfaces, thus preserving the Schottky barrier height and ultimately, the outstanding performance of the transistor. This device is fully integrated into silicon after standard CMOS-compatible processing, so that it could be easily adopted into front-end-of-line or even in back-end-of-line stages of an integrated circuit, where low thermal budget is required and where its functionality could be increased by developing additional and fast logic.

Au Nanoparticles/HfO2/Fully Depleted Silicon-on-Insulator MOSFET Enabled Rapid Detection of Zeptomole COVID-19 Gene With Electrostatic Enrichment Process.

In this work, a novel sensing structure based on Au nanoparticles/HfO2/fully depleted silicon-on-insulator (AuNPs/HfO2/FDSOI) MOSFET is fabricated. Using such a planar double gate MOSFET, the electrostatic enrichment (ESE) process is proposed for the ultrasensitive and rapid detection of the coronavirus disease 2019 (COVID-19) ORF1ab gene. The back-gate (BG) bias can induce the required electric field that enables the ESE process in the testing liquid analyte with indirect contact with the top-Si layer. It is revealed that the ESE process can rapidly and effectively accumulate ORF1ab genes close to the HfO2 surface, which can significantly change the MOSFET threshold voltage ([Formula: see text]). The proposed MOSFET successfully demonstrates the detection of zeptomole (zM) COVID-19 ORF1ab gene with an ultralow detection limit down to 67 zM (~0.04 copy/[Formula: see text]) for a test time of less than 15 min even in a high ionic-strength solution. Besides, the quantitative dependence of [Formula: see text] variation on COVID-19 ORF1ab gene concentration from 200 zM to 100 femtomole is also revealed, which is further confirmed by TCAD simulation.

General Purpose Transistor Characterized as Dosimetry Sensor of Proton Beams.

A commercial pMOS transistor (MOSFET), 3N163 from Vishay (USA), has been characterized as a low-energy proton beam dosimeter. The top of the samples' housing has been removed to guarantee that protons reached the sensitive area, that is, the silicon die. Irradiations took place at the National Accelerator Centre (Seville, Spain). During irradiations, the transistors were biased to improve the sensitivity, and the silicon temperature was monitored activating the parasitic diode of the MOSFET. Bias voltages of 0, 1, 5, and 10 V were applied to four sets of three transistors, obtaining an averaged sensitivity that was linearly dependent on this voltage. In addition, the short-fading effect was studied, and the uncertainty of this effect was obtained. The bias voltage that provided an acceptable sensitivity, (11.4 ± 0.9) mV/Gy, minimizing the uncertainty due to the fading effect (-0.09 ± 0.11) Gy was 1 V for a total absorbed dose of 40 Gy. Therefore, this off-the-shelf electronic device presents promising characteristics as a dosimeter sensor for proton beams.

A Novel Dielectric Modulated Gate-Stack Double-Gate Metal-Oxide-Semiconductor Field-Effect Transistor-Based Sensor for Detecting Biomolecules.

In this article, the performance of n-type junctionless (JL) double-gate (DG) MOSFET-based biosensors with and without gate stack (GS) has been studied. Here, the dielectric modulation (DM) method is applied to detect biomolecules in the cavity. The sensitivity of n-type JL-DM-DG-MOSFET and n-type JL-DM-GSDG-MOSFET-based biosensors have also been evaluated. The sensitivity (ΔVth) improved in JL-DM-GSDG MOSFET/JL-DM-DG-MOSFET-based biosensors for neutral/charged biomolecules is 116.66%/66.66% and 1165.78%/978.94%, respectively, compared with the previously reported results. The electrical detection of biomolecules is validated using the ATLAS device simulator. The noise and analog/RF parameters are compared between both biosensors. A lower threshold voltage is observed in the GSDG-MOSFET-based biosensor. The Ion/Ioff ratio is higher for DG-MOSFET-based biosensors. The proposed GSDG-MOSFET-based biosensor demonstrates higher sensitivity than the DG-MOSFET-based biosensor. The GSDG-MOSFET-based biosensor is suitable for low-power, high-speed, and high sensitivity applications.

Random Telegraph Noise Degradation Caused by Hot Carrier Injection in a 0.8 µm-Pitch 8.3Mpixel Stacked CMOS Image Sensor.

In this work, the degradation of the random telegraph noise (RTN) and the threshold voltage (Vt) shift of an 8.3Mpixel stacked CMOS image sensor (CIS) under hot carrier injection (HCI) stress are investigated. We report for the first time the significant statistical differences between these two device aging phenomena. The Vt shift is relatively uniform among all the devices and gradually evolves over time. By contrast, the RTN degradation is evidently abrupt and random in nature and only happens to a small percentage of devices. The generation of new RTN traps by HCI during times of stress is demonstrated both statistically and on the individual device level. An improved method is developed to identify RTN devices with degenerate amplitude histograms.

Radiation exposure in cone beam CT measured using a MOSFET and RPLGD dosimeter and Monte Carlo simulation in phantom.

BACKGROUND: Due to the wide application of the cone beam computed tomography (CBCT) in clinical practice, it is important to assess radiation dose of CBCT more accurately and efficiently in different clinical applications. OBJECTIVE: This study aims to calculate effective and absorbed doses in CBCT measured in an anthropomorphic phantom using computer-based Monte Carlo (PCXMC) software, and to conduct comparative evaluations of MOSFET (metal- oxide- semiconductor field-effect transistor) and radiophotoluminescence glass dosimeters (RPLGD). METHODS: Effective and absorbed organ doses are compared with those obtained using MOSFET and RPLGD dosimetry in an anthropomorphic phantom given the same exposure settings. Effective and absorbed organ doses from CBCT during scout and main projections are calculated using PCXMC and PCXMCRotation software, respectively. RESULTS: The mean effective dose from CBCT calculated using PCXMC software is 233.8µSv, while the doses calculated using dosimetry (MOSFET and RPLGD) are 266.67µSv and 268.78µSv, respectively. The X-ray source variation is 0.79%. The prescription limits based on the Friedman test for MOSFET and RPLGD pre-points (i.e., in an analytical analysis of diagnostic names in CBCT) are not statistically significant. The calculated correlation coefficient between MOSFET- and RPLGD-derived absorbed dose values with respect to a field of view CBCT parameter of 17×13.5 mm is r = 0.8623. CONCLUSIONS: The study demonstrates that the PCXMC software may be used as an alternative to MOSFET and RPLGD dosimetry for effective and absorbed organ dose estimation in CBCT conducted with a large FOV in an anthropomorphic phantom.

Performance enhancement of GaSb vertical nanowire p-type MOSFETs on Si by rapid thermal annealing.

GaSb is considered as an attractive p-type channel material for future III-V metal-oxide-semiconductor (MOS) technologies, but the processing conditions to utilize the full device potential such as low power logic applications and RF applications still need attention. In this work, applying rapid thermal annealing (RTA) to nanoscale GaSb vertical nanowire p-type MOS field-effect transistors, we have improved the average peak transconductance (gm,peak) by 50% among 28 devices and achieved 70µSµm-1atVDS = -0.5 V in a device with 200 nm gate length. In addition, a low subthreshold swing down to 144 mV dec-1as well as an off-current below 5 nAµm-1which refers to the off-current specification in low-operation-power condition has been obtained. Based on the statistical analysis, the results show a great enhancement in both on- and off-state performance with respect to previous work mainly due to the improved electrostatics and contacts after RTA, leading to a potential in low-power logic applications. We have also examined a short channel device withLg = 80 nm in RTA, which shows an increasedgm,peakup to 149µSµm-1atVDS = -0.5 V as well as a low on-resistance of 4.7 kΩ·µm. The potential of further enhancement ingmvia RTA offers a good alternative to obtain high-performance devices for RF applications which have less stringent requirement for off-state performance. Our results indicate that post-fabrication annealing provides a great option to improve the performance of GaSb-based p-type devices with different structures for various applications.

Probing hole spin transport of disorder quantum dots via Pauli spin-blockade in standard silicon transistors.

Single hole transport and spin detection is achievable in standard p-type silicon transistors owing to the strong orbital quantization of disorder based quantum dots. Through the use of the well acting as a pseudo-gate, we discover the formation of a double-quantum dot system exhibiting Pauli spin-blockade and investigate the magnetic field dependence of the leakage current. This enables attributes that are key to hole spin state control to be determined, where we calculate a tunnel couplingtcof 57µeV and a short spin-orbit lengthlSOof 250 nm. The demonstrated strong spin-orbit interaction at the interface when using disorder based quantum dots supports electric-field mediated control. These results provide further motivation that a readily scalable platform such as industry standard silicon technology can be used to investigate interactions which are useful for quantum information processing.

In-vivo dose measurements with MOSFET dosimeters during MV portal imaging.

BACKGROUND: The purpose of this study was to investigate the feasibility of MOSFET dosimeter in measuring eye dose during 2D MV portal imaging for setup verification in radiotherapy. MATERIALS AND METHODS: The in-vivo dose measurements were performed by placing the dosimeters over the eyes of 30 brain patients during the acquisition of portal images in linear accelerator by delivering 1 MU with the field sizes of 10 × 10 cm2 and 15 × 15 cm2. RESULTS: The mean doses received by the left and right eyes of 10 out of 30 patients when both eyes were completely inside the anterior portal field were found to be 2.56 ± 0.2 cGy and 2.75 ± 0.2, respectively. Similarly, for next 10 patients out of the same 30 patients the mean doses to left and right eyes when both eyes were completely out of the anterior portal fields were found to be 0.13 ± 0.02 cGy and 0.17 ± 0.02 cGy, respectively. The mean doses to ipsilateral and contralateral eye for the last 10 patients when one eye was inside the anterior portal field were found to be 3.28 ± 0.2 cGy and 0.36 ± 0.1 cGy, respectively. CONCLUSION: The promising results obtained during 2D MV portal imaging using MOSFET have shown that this dosimeter is well suitable for assessing low doses during imaging thereby enabling to optimize the imaging procedure using the dosimetric data obtained. In addition, the documentation of the dose received by the patient during imaging procedure is possible with the help of an in-built software in conjunction with the MOSFET reader module.

MOSFET dosimeter characterization in MR-guided radiation therapy (MRgRT) Linac.

PURPOSE: With the increasing use of MR-guided radiation therapy (MRgRT), it becomes important to understand and explore accuracy of medical dosimeters in the presence of magnetic field. The purpose of this work is to characterize metal-oxide-semiconductor field-effect transistors (MOSFETs) in MRgRT systems at 0.345 T magnetic field strength. METHODS: A MOSFET dosimetry system, developed by Best Medical Canada for in-vivo patient dosimetry, was used to study various commissioning tests performed on a MRgRT system, MRIdian® Linac. We characterized the MOSFET dosimeter with different cable lengths by determining its calibration factor, monitor unit linearity, angular dependence, field size dependence, percentage depth dose (PDD) variation, output factor change, and intensity modulated radiation therapy quality assurance (IMRT QA) verification for several plans. MOSFET results were analyzed and compared with commissioning data and Monte Carlo calculations. RESULTS: MOSFET measurements were not found to be affected by the presence of 0.345 T magnetic field. Calibration factors were similar for different cable length dosimeters either placed at the parallel or perpendicular direction to the magnetic field, with variations of less than 2%. The detector showed good linearity (R2  = 0.999) for 100-600 MUs range. Output factor measurements were consistent with ionization chamber data within 2.2%. MOSFET PDD measurements were found to be within 1% for 1-15 cm depth range in comparison to ionization chamber. MOSFET normalized angular response matched thermoluminescent detector (TLD) response within 5.5%. The IMRT QA verification data for the MRgRT linac showed that the percentage difference between ionization chamber and MOSFET was 0.91%, 2.05%, and 2.63%, respectively for liver, spine, and mediastinum. CONCLUSION: MOSFET dosimeters are not affected by the 0.345 T magnetic field in MRgRT system. They showed physics parameters and performance comparable to TLD and ionization chamber; thus, they constitute an alternative to TLD for real-time in-vivo dosimetry in MRgRT procedures.

Fundamental research on semiconductor SiC and its applications to power electronics.

Today, the silicon carbide (SiC) semiconductor is becoming the front runner in advanced power electronic devices. This material has been considered to be useful for abrasive powder, refractory bricks as well as ceramic varistors. Big changes have occurred owing to the author's inspirational idea in 1968 to "make transistors from unusual material". The current paper starts by describing the history of SiC research involving fundamental studies by the author's group: unique epitaxial crystal growth techniques, the physical characterization of grown layers and processes for device fabrication. Trials for fabricating SiC power devices and their characteristics conducted until 2004 are precisely described. Recent progress in SiC crystal growth and peripheral techniques for SiC power devices are introduced. Finally, the present progress concerning SiC power devices is introduced together with the implementation of those devices in society.

Characteristics Research of a High Sensitivity Piezoelectric MOSFET Acceleration Sensor.

In order to improve the output sensitivity of the piezoelectric acceleration sensor, this paper proposed a high sensitivity acceleration sensor based on a piezoelectric metal oxide semiconductor field effect transistor (MOSFET). It is constituted by a piezoelectric beam and an N-channel depletion MOSFET. A silicon cantilever beam with Pt/ZnO/Pt/Ti multilayer structure is used as a piezoelectric beam. Based on the piezoelectric effect, the piezoelectric beam generates charges when it is subjected to acceleration. Due to the large input impedance of the MOSFET, the charge generated by the piezoelectric beam can be used as a gate control signal to achieve the purpose of converting the output charge of the piezoelectric beam into current. The test results show that when the external excitation acceleration increases from 0.2 g to 1.5 g with an increment of 0.1 g, the peak-to-peak value of the output voltage of the proposed sensors increases from 0.327 V to 2.774 V at a frequency of 1075 Hz. The voltage sensitivity of the piezoelectric beam is 0.85 V/g and that of the proposed acceleration sensor was 2.05 V/g, which is 2.41 times higher than the piezoelectric beam. The proposed sensor can effectively improve the voltage output sensitivity and can be used in the field of structural health monitoring.

Temperature-Dependent Transport in Ultrathin Black Phosphorus Field-Effect Transistors.

We studied the temperature-dependent transport properties of ultrathin black phosphorus (BP). We present measurements of BP Schottky barrier (SB) metal-oxide-semiconductor field-effect-transistors (MOSFETs) with various channel lengths, constructed from a single BP sample with nanoscale uniformity in thickness and width. The electrical characterization reveals a reversal in the temperature dependence of drain current as a function of gate voltage. This reversal indicates a transition in the charge conduction limiting mechanisms as the device is swept from the off-state into the on-state. In the off-state, charge transport is limited by thermionic emission over the energy barriers at the source/drain SB contacts, and drain current increases with temperature. In the on-state, carriers can easily tunnel across the SB at the contacts, and charge transport is limited by scattering in the channel. As a result, drain current decreases with temperature in the on-state, as scattering increases with temperature. Using Landauer transport theory, we derive a closed-form expression for thermionic emission current in SB-MOSFETs with two-dimensional channels. We use this expression to extract the SB height at metal contact interface with BP and demonstrate the impact of scattering on the extraction. We then use a comprehensive BP SB-MOSFET model to analyze on-state current as a function of temperature and demonstrate the effects of charged impurity and phonon scattering on the transport properties of BP through extractions of mobility at fixed carrier density.

Gate Quantum Capacitance Effects in Nanoscale Transistors.

As the physical dimensions of a transistor gate continue to shrink to a few atoms, performance can be increasingly determined by the limited electronic density of states (DOS) in the gate and the gate quantum capacitance (CQ). We demonstrate the impact of gate CQ and the dimensionality of the gate electrode on the performance of nanoscale transistors through analytical electrostatics modeling. For low-dimensional gates, the gate charge can limit the channel charge, and the transfer characteristics of the device become dependent on the gate DOS. We experimentally observe for the first time, room-temperature gate quantization features in the transfer characteristics of single-walled carbon nanotube (CNT)-gated ultrathin silicon-on-insulator (SOI) channel transistors; features which can be attributed to the Van Hove singularities in the one-dimensional DOS of the CNT gate. In addition to being an important aspect of future transistor design, potential applications of this phenomenon include multilevel transistors with suitable transfer characteristics obtained via engineered gate DOS.

Deep Submicron EGFET Based on Transistor Association Technique for Chemical Sensing.

Extended-gate field-effect transistor (EGFET) is an electronic interface originally developed as a substitute for an ion-sensitive field-effect transistor (ISFET). Although the literature shows that commercial off-the-shelf components are widely used for biosensor fabrication, studies on electronic interfaces are still scarce (e.g., noise processes, scaling). Therefore, the incorporation of a custom EGFET can lead to biosensors with optimized performance. In this paper, the design and characterization of a transistor association (TA)-based EGFET was investigated. Prototypes were manufactured using a 130 nm standard complementary metal-oxide semiconductor (CMOS) process and compared with devices presented in recent literature. A DC equivalence with the counterpart involving a single equivalent transistor was observed. Experimental results showed a power consumption of 24.99 mW at 1.2 V supply voltage with a minimum die area of 0.685 × 1.2 mm². The higher aspect ratio devices required a proportionally increased die area and power consumption. Conversely, the input-referred noise showed an opposite trend with a minimum of 176.4 nVrms over the 0.1 to 10 Hz frequency band for a higher aspect ratio. EGFET as a pH sensor presented further validation of the design with an average voltage sensitivity of 50.3 mV/pH, a maximum current sensitivity of 15.71 mA1/2/pH, a linearity higher than 99.9%, and the possibility of operating at a lower noise level with a compact design and a low complexity.

GaN-Based Ultraviolet Passive Pixel Sensor on Silicon (111) Substrate.

The fabrication of a single pixel sensor, which is a fundamental element device for the fabrication of an array-type pixel sensor, requires an integration technique of a photodetector and transistor on a wafer. In conventional GaN-based ultraviolet (UV) imaging devices, a hybrid-type integration process is typically utilized, which involves a backside substrate etching and a wafer-to-wafer bonding process. In this work, we developed a GaN-based UV passive pixel sensor (PPS) by integrating a GaN metal-semiconductor-metal (MSM) UV photodetector and a Schottky-barrier (SB) metal-oxide-semiconductor field-effect transistor (MOSFET) on an epitaxially grown GaN layer on silicon substrate. An MSM-type UV sensor had a low dark current density of 3.3 × 10-7 A/cm² and a high UV/visible rejection ratio of 10³. The GaN SB-MOSFET showed a normally-off operation and exhibited a maximum drain current of 0.5 mA/mm and a maximum transconductance of 30 µS/mm with a threshold voltage of 4.5 V. The UV PPS showed good UV response and a high dark-to-photo contrast ratio of 10³ under irradiation of 365-nm UV. This integration technique will provide one possible way for a monolithic integration of the GaN-based optoelectronic devices.