Prediction of electrical properties of GAAFET based on integrated learning model.

As device feature sizes continue to decrease and fin field effect transistors reach their physical limits, gate all around field effect transistors (GAAFETs) have emerged with larger gate control areas and stackable characteristics for better suppression of second-order effects such as short-channel effects due to their gate encircling characteristics. Traditional methods for studying the electrical characteristics of devices are mostly based on the technology computer-aided design. Still, it is not conducive to developing new devices due to its time-consuming and inefficient drawbacks. Deep learning (DL) and machine learning (ML) have been well-used in recent years in many fields. In this paper, we propose an integrated learning model that integrates the advantages of DL and ML to solve many problems in traditional methods. This integrated learning model predicts the direct current characteristics, capacitance characteristics, and electrical parameters of GAAFET better than those predicted by DL or ML methods alone, with a linear regression factor (R2) greater than 0.99 and very small root mean square error. The proposed integrated learning model achieves fast and accurate prediction of GAAFET electrical characteristics, which provides a new idea for device and circuit simulation and characteristics prediction in microelectronics.

Hemorrhagic cystitis induced by JC polyomavirus infection following COVID-19: a case report.

JC polyomavirus (JCPyV) is a human polyomavirus that can establish lifelong persistent infection in the majority of adults. It is typically asymptomatic in immunocompetent individuals. However, there is a risk of developing progressive multifocal leukoencephalopathy (PML) in immunocompromised or immunosuppressed patients. Though JCPyV commonly resides in the kidney-urinary tract, its involvement in urinary system diseases is extremely rare. Here, we reported a case of a 60-year-old male patient with coronavirus disease 2019 (COVID-19) infection who developed hemorrhagic cystitis after receiving treatment with nirmatrelvir 300 mg/ritonavir 100 mg quaque die (QD). Subsequent metagenomic next-generation sequencing (mNGS) confirmed the infection to be caused by JCPyV type 2. Then, human immunoglobulin (PH4) for intravenous injection at a dose of 25 g QD was administered to the patient. Three days later, the hematuria resolved. This case illustrates that in the setting of compromised host immune function, JCPyV is not limited to causing central nervous system diseases but can also exhibit pathogenicity in the urinary system. Moreover, mNGS technology facilitates rapid diagnosis of infectious etiology by clinical practitioners, contributing to precise treatment for patients.

Random Skin Biopsy for Diagnosis of Intravascular Large B-Cell Lymphoma: A Case Report and Literature Review.

BACKGROUND: Intravascular large B-cell lymphoma (IVLBCL) is a rare, aggressive B-cell lymphoma. The heterogeneity of its clinical symptoms makes it hard to be diagnosed. The diagnosis is followed by pathological examination of affected tissues and organs including skin, central nervous system, and bone marrow. Random skin biopsy (RSB) with high sensitivity and less invasiveness becomes a common method for diagnosis in suspected patients without skin lesions. CASE REPORT: We reported the case of a 67-year-old man who complained of fever, dizziness, unsteady gait, numbness in both lower extremities, and incontinence. Blood routine examination suggested elevated levels of lactate dehydrogenase. Enhanced magnetic resonance imaging of the head and thoracolumbosacral spine, next-generation sequencing in blood, cerebrospinal fluid collection, bone marrow aspiration, and positron emission tomography-computed tomography presented no evidence of solid tumors. However, there were intravascular tumor cell growth and morphosis as determined by RSB. CD20, CD79a, CD5, BCL-6, and BCL-2 were positive as tested by immunohistochemistry, and Ki-67 showed high proliferative activity. Taking the medical history as an element, the patient received a diagnosis of IVLBCL. After he completed 3 cycles of RCDOP + orelabrutinib, his general condition improved. CONCLUSION: IVLBCL is an aggressive, lethal cancer that is difficult to diagnose; therefore, it is recommended for the suspected patients to receive RSB promptly and early treatment at the earliest opportunity to achieve amelioration in prognosis.

128-pixel arrays of 4H-SiC UV APD with dual-frequency PECVD SiNx passivation.

In this paper, high-performance 1×128 linear arrays of 4H-SiC ultraviolet (UV) avalanche photodiode (APD) with dual-frequency plasma enhanced chemical vapor deposition (PECVD) passivation are demonstrated for the first time. The results show that SiNx dielectric deposited by dual-frequency PECVD can effectively reduce the leakage current at high bias voltages. Due to the improved 4H-SiC epi-layer material and SiNx passivation, the fabricated 22 mm-long 1×128 4H-SiC APD linear arrays exhibit an excellent performance with a high pixel yield of 100% and a small breakdown voltage variation of 0.2 V, which is the best result ever reported. At room temperature, the pixels have a gain of over 105 and a maximum quantum efficiency of 53.5% @ 285 nm. Besides the high uniformity of breakdown voltage for 128 pixels, the dark currents at 95% of breakdown voltage are all below 1 nA.

Comprehensively Improved Performance of ß-Ga2O3 Solar-Blind Photodetector Enabled by a Homojunction with Unique Passivation Mechanisms.

Ga2O3-based solar-blind photodetectors have been extensively investigated for a wide range of applications. However, to date, a lot of research has focused on optimizing the epitaxial technique or constructing a heterojunction, and studies concerning surface passivation, a key technique in electronic and optoelectronic devices, are severely lacking. Here, we report an ultrasensitive metal-semiconductor-metal photodetector employing a ß-Ga2O3 homojunction structure realized by low-energy surface fluorine plasma treatment, in which an ultrathin fluorine-doped layer served for surface passivation. Without inserting/capping a foreign layer, this strategy utilized fluorine dopants to both passivate local oxygen vacancies and suppress surface chemisorption. The dual effects have opposite impacts on device current magnitude (by suppressing metal/semiconductor junction leakage and inhibiting surface-chemisorption-induced carrier consumption) but dominate in dark and under illumination, respectively. By means of such unique mechanisms, the simultaneous improvement on dark and photo current characteristics was achieved, leading to the sensitivity enhanced by nearly 1 order of magnitude. Accordingly, the 15 min treated sample exhibited striking competitiveness in terms of comprehensive properties, including a dark current as low as 6 pA, a responsivity of 18.43 A/W, an external quantum efficiency approaching 1 × 104%, a specific detectivity of 2.48 × 1014 Jones, and a solar-blind/UV rejection ratio close to 1 × 105. Furthermore, the response speed was effectively accelerated because of the reduction on metal/semiconductor interface trap states. Our findings provide a facile, economical, and contamination-free surface passivation technique, which unlocks the potential for comprehensively improving the performance of ß-Ga2O3 solar-blind metal-semiconductor-metal photodetectors.

A novel AlGaN/GaN heterostructure field-effect transistor based on open-gate technology.

In this study, a novel AlGaN/GaN heterostructure field-effect transistor based on open-gate technology was fabricated. Sample transistors of different structures and sizes were constructed. Through measurements, it was found that by changing the width of the opening, the threshold voltage of the device could be easily modulated across a larger range. The open-gate device had two working modes with different transconductance. When the gate-source voltage VGS ≤ - 4.5 V, only the open region was conductive, and a new working mechanism modulated the channel current. Corresponding theoretical analysis and calculations showed that its saturation mechanism was related to a virtual gate formed by electron injection onto the surface. Also, the gate-source voltage modulated the open channel current by changing the channel electron mobility through polarization Coulomb field scattering. When used as class-A voltage amplifiers, open-gate devices can achieve effective voltage amplification with very low power consumption.

Improved Linearity with Polarization Coulomb Field Scattering in AlGaN/GaN Heterostructure Field-Effect Transistors.

The single-tone power of the AlGaN/GaN heterostructure field-effect transistors (HFETs) with different gate widths was measured. A distinct improvement in device linearity was observed in the sample with a larger gate width. The analysis of the variation of the parasitic source access resistance showed that, as the gate bias is increased, the polarization Coulomb field scattering can offset the increased polar optical phonon scattering and improve the device linearity. This approach is shown to be effective in improving the device linearity of AlGaN/GaN HFETs.

Effect of Polarization Coulomb Field Scattering on Electrical Properties of the 70-nm Gate-Length AlGaN/GaN HEMTs.

This research presents the first experimental observation of the enhancement of the polarization Coulomb field (PCF) scattering by aggressive lateral scaling of GaN HEMTs. By decreasing the source-drain distance to 300 nm through n+-GaN ohmic regrowth, 70-nm gate AlGaN/GaN HEMTs achieved an extremely low electron mobility. Different from the electron mobility of the traditional device, which was determined by polar optical phonon scattering, the electron mobility of the 70-nm gate AlGaN/GaN HEMTs was dominated by PCF scattering due to the enhanced nonuniform strain distribution of the AlGaN barrier layer. Furthermore, compared with the parasitic access resistance at gate-source voltage VGS = 0 V, the parasitic access resistance at VGS = -2.5 V showed an increase of approximately 700%, which was also responsible for the enhanced PCF scattering.

Effect of Different Gate Lengths on Polarization Coulomb Field Scattering Potential in AlGaN/GaN Heterostructure Field-Effect Transistors.

The AlGaN/GaN heterostructure field-effect transistors with different gate lengths were fabricated. Based on the chosen of the Hamiltonian of the system and the additional polarization charges, two methods to calculate PCF scattering by the scattering theory were presented. By comparing the measured and calculated source-drain resistances, the effect of the different gate lengths on the PCF scattering potential was confirmed.

Hot electron induced non-saturation current behavior at high electric field in InAlN/GaN heterostructures with ultrathin barrier.

The high-field transport characteristics of nearly lattice-matched InAlN/GaN heterostructures with different barrier thickness were investigated. It is found that the current in the InAlN/GaN heterostructures with ultrathin barrier shows unsaturated behaviors (or secondary rising) at high voltage, which is different from that of AlGaN/GaN heterostructures. This phenomenon is more obvious if the barrier thickness is thinner and the channel width is narrower. The experimental results demonstrate that it is the increasing carrier density excited from the more defect states by the hot electrons with larger electron saturation velocity that results in the unsaturated current behaviors in InAlN/GaN heterostructures. Our results pave a way for further optimizing InAlN barrier design and improving the reliability of InAlN/GaN HEMTs.

Influence of the ratio of gate length to drain-to-source distance on the electron mobility in AlGaN/AlN/GaN heterostructure field-effect transistors.

Using measured capacitance-voltage curves with different gate lengths and current-voltage characteristics at low drain-to-source voltage for the AlGaN/AlN/GaN heterostructure field-effect transistors (HFETs) of different drain-to-source distances, we found that the dominant scattering mechanism in AlGaN/AlN/GaN HFETs is determined by the ratio of gate length to drain-to-source distance. For devices with small ratio (here, less than 1/2), polarization Coulomb field scattering dominates electron mobility. However, for devices with large ratio (here, more than 1/2), longitudinal optical (LO) phonon scattering and interface roughness scattering are dominant. The reason is closely related to polarization Coulomb field scattering.