97 research outputs found
Characterization and TCAD Modeling of Mixed-Mode Stress Induced by Impact Ionization in Scaled SiGe HBTs
We investigate the reliability of state-of-the-art SiGe heterojunction bipolar transistors (HBTs) in 55-nm technology under mixed-mode stress. We perform electrical characterization and implement a TCAD model calibrated on the measurement data to describe the increased base current degradation at different collector-base voltages. We introduce a simple and self-consistent simulation methodology that links the observed degradation trend to interface traps generation at the emitter/base spacer oxide ascribed to hot holes generated by impact ionization (II) in the collector/base depletion region. This effectively circumvents the limitations of commercial TCAD tools that do not allow II to be the driving force of the degradation. The approach accounts for self-heating and electric fields distribution allowing to reproduce measurement data including the deviation from the power-law behavior
On the Modeling of the Donor/Acceptor Compensation Ratio in CarbonâDoped GaN to Univocally Reproduce Breakdown Voltage and Current Collapse in Lateral GaN Power HEMTs
The intentional doping of lateral GaN power high electron mobility transistors (HEMTs)
with carbon (C) impurities is a common technique to reduce buffer conductivity and increase
breakdown voltage. Due to the introduction of trap levels in the GaN bandgap, it is well known that
these impurities give rise to dispersion, leading to the soâcalled âcurrent collapseâ as a collateral
effect. Moreover, firstâprinciples calculations and experimental evidence point out that C introduces
trap levels of both acceptor and donor types. Here, we report on the modeling of the donor/acceptor
compensation ratio (CR), that is, the ratio between the density of donors and acceptors associated
with C doping, to consistently and univocally reproduce experimental breakdown voltage (VBD) and
currentâcollapse magnitude (ÎICC). By means of calibrated numerical device simulations, we
confirm that ÎICC is controlled by the effective trap concentration (i.e., the difference between the
acceptor and donor densities), but we show that it is the total trap concentration (i.e., the sum of
acceptor and donor densities) that determines VBD, such that a significant CR of at least 50%
(depending on the technology) must be assumed to explain both phenomena quantitatively. The
results presented in this work contribute to clarifying several previous reports, and are helpful to
device engineers interested in modeling Câdoped lateral GaN power HEMTs
The effects of carbon on the bidirectional threshold voltage instabilities induced by negative gate bias stress in GaN MIS-HEMTs
In this paper, numerical device simulations are used to point out the possible contributions of carbon doping to the threshold voltage instabilities induced by negative gate bias stress in AlGaN/GaN metalâinsulatorâsemiconductor high-electron
mobility transistors. It is suggested that carbon can have a role in both negative and positive threshold voltage shifts, as a
result of (1) the changes in the total negative charge stored in the carbon-related acceptor traps in the GaN buffer, and (2)
the attraction of carbon-related free holes to the device surface and their capture into interface traps or recombination with
gate-injected electrons. For a proper device optimization of carbon-doped MIS-HEMTs, it is therefore important to take
these mechanisms into account, in addition to those related to defects in the gate dielectric volume and interface which are
conventionally held responsible for threshold voltage instabilities
Reliable Prediction of Post-Operative Complicationsâ Rate Using the G8 Screening Tool: A Prospective Study on Elderly Patients Undergoing Surgery for Kidney Cancer
Abstract: In the last years the incidence of renal neoplasms has been steadily increasing, along with
the average age of patients at the time of diagnosis. Surgical management for localized disease is
becoming more challenging because of patientsâ frailty. We conducted a multi-center prospective
study to evaluate the role of the G8 as a screening tool in the assessment of intra and post-operative
complications of elderly patients (â70 y.o.) undergoing surgery for kidney cancer. A total of
162 patients were prospectively enrolled between January 2015 to January 2019 and divided into
two study groups (frail vs. not-frail) according to their geriatric risk profile based on G8 score.
Several factors (i.e., age, CCI, ASA score, preoperative anemia, RENAL score, surgical procedures,
and techniques) were analyzed to identify whether any of them would configure as a statistically
significant predictor of surgical complications. According to the G8 Score, 90 patients were included
in the frail group. A total of 52 frail patients vs. 4 non-frail patients developed a postoperative
complication of any kind (p < 0.001). Of these, 11 were major complications and all occurred in the
frail group. Our results suggest that the G8 screening tool is an effective and useful instrument to
predict the risk of overall complications in elderly patients prior to renal surgery
Responses of peripheral blood mononucleated cells from non-celiac gluten sensitive patients to various cereal sources
Non-celiac gluten sensitivity (NCGS) is still an undefined syndrome whose triggering mechanisms remain unsettled. This study aimed to clarify how cultured peripheral blood mononucleated cells (PBMC) obtained from NCGS patients responded to contact with wheat proteins. Results demonstrated that wheat protein induced an overactivation of the proinflammatory chemokine CXCL10 in PBMC from NCGS patients, and that the overactivation level depends on the cereal source from which proteins are obtained. CXCL10 is able to decrease the transepithelial resistance of monolayers of normal colonocytes (NCM 460) by diminishing the mRNA expression of cadherin-1 (CDH1) and tight junction protein 2 (TJP2), two primary components of the tight junction strands. Thus, CXCL10 overactivation is one of the mechanisms triggered by wheat proteins in PBMC obtained from NCGS patients. This mechanism is activated to a greater extent by proteins from modern with respect to those extracted from ancient wheat genotypes
Targeted activation of the SHP-1/PP2A signaling axis elicits apoptosis of chronic lymphocytic leukemia cells
Lyn, a member of the Src family of kinases, is a key factor in the dys-regulation of survival and apoptotic pathways of malignant B cells in chronic lymphocytic leukemia. One of the effects of Lyn's action is spatial and functional segregation of the tyrosine phosphatase SHP-1 into two pools, one beneath the plasma membrane in an active state promoting pro-survival signals, the other in the cytosol in an inhibited conformation and unable to counter the elevated level of cytosolic tyrosine phosphorylation. We herein show that SHP-1 activity can be elicited directly by nintedanib, an agent also known as a triple angiokinase inhibitor, circumventing the phospho-S591-dependent inhibition of the phosphatase, leading to the dephosphorylation of pro-apoptotic players such as procaspase-8 and serine/threonine phosphatase 2A, eventually triggering apoptosis. Furthermore, the activation of PP2A by using MP07-66, a novel FTY720 analog, stimulated SHP-1 activity via dephosphorylation of phospho-S591, which unveiled the existence of a positive feedback signaling loop involving the two phosphatases. In addition to providing further insights into the molecular basis of this disease, our findings indicate that the PP2A/SHP-1 axis may emerge as an attractive, novel target for the development of alternative strategies in the treatment of chronic lymphocytic leukemia
West Nile virus transmission with human cases in Italy, August - September 2009.
In 2009, to date 16 human cases of West Nile neuroinvasive disease (WNND) have been reported in Italy, in three regions: Veneto, Emilia-Romagna and Lombardia. The number of cases is higher compared with last year when nine cases were identified (eight cases of WNND and one case of West Nile fever) and the geographical distribution indicates spread from east to west
- âŚ