Search results for "AlGaN"

Multi-pulse characterization of trapping/detrapping mechanisms in AlGaN/GaN high electromobility transistors

2019

GaN high-electro mobility transistors (HEMTs) are among the most promising candidates for use in high-power, high-frequency, and high-temperature electronics owing to their high electrical breakdown threshold and their high saturation electron velocity. The applications of these AlGaN/GaN HEMTs in power converters are limited by the surface trapping effects of drain-current collapse. Charge-trapping mechanisms affect the dynamic performance of all GaN HEMTs used in power switching applications. This study analyzes the dynamic resistance of GaN HEMTs and finds that the effects of dynamic resistance can be suppressed by controlling switching conditions and on-off cycles.

Monitoring of Trough Plasma Ganciclovir Levels and Peripheral Blood Cytomegalovirus (CMV)-Specific CD8 + T Cells To Predict CMV DNAemia Clearance in …

2014

ABSTRACT It is uncertain whether monitoring plasma ganciclovir (GCV) levels is useful in predicting cytomegalovirus (CMV) DNAemia clearance in preemptively treated allogeneic stem cell transplant recipients. In this observational study, including 13 episodes of CMV DNAemia treated with intravenous (i.v.) GCV or oral valganciclovir, we showed that monitoring trough plasma GCV levels does not reliably predict response to therapy. Rather, immunological monitoring (pp65 and immediate-early [IE]-1-specific gamma interferon [IFN-γ]-producing CD8 + T cells) appeared to perform better for this purpose.

Effect of long-term prophylaxis in the development of cytomegalovirus-specific T-cell immunity in D+/R- solid organ transplant recipients.

2015

Background This study aimed to characterize the dynamics of acquisition of cytomegalovirus (CMV)-specific cell-mediated immunity (CMI) in CMV donor positive/recipient negative solid organ transplant (SOT) patients receiving long-term antiviral prophylaxis, and to determine whether development of CMI confers protection against CMV disease. Methods A prospective multicenter study was conducted in Spain from September 2009 to September 2012. Whole blood specimens were prospectively collected at 30, 90, 120, 200, and 365 days after SOT, and CMI was determined by enumeration of CMV pp65 and IE-1-specific CD69+/interferon-γ-producing CD8+ and CD4+ T cells by flow cytometry for intracellular cytok…

Cytomegalovirus prevention strategies in seropositive kidney transplant recipients: an insight into current clinical practice

2015

Producción Científica

Metal/Semiconductor Barrier Properties of Non-Recessed Ti/Al/Ti and Ta/Al/Ta Ohmic Contacts on AlGaN/GaN Heterostructures

2019

This paper compares the metal/semiconductor barrier height properties of non-recessed Ti/Al/Ti and Ta/Al/Ta contacts on AlGaN/GaN heterostructures. Both contacts exhibited a rectifying behavior after deposition and after annealing at temperatures up to 550 &deg

DI-032 Study of effectiveness and safety of foscarnet in cytomegalovirus treatment in haematopoietic stem cell transplantation recipients

2016

Background Cytomegalovirus disease is an important cause of morbidity and mortality in haematopoietic stem cell transplantation (HSCT) recipients. Foscarnet, an intravenous drug active against cytomegalovirus, represents an increasingly widespread alternative when there is resistance or intolerance to conventional treatments (ganciclovir/valganciclovir, acyclovir). More data about its use, effectiveness and safety in the clinical practice are necessary. Purpose To analyse the effectiveness and safety of the use of foscarnet against cytomegalovirus in HSCT recipients, and its adaptation to clinical practice guidelines and expert recommendations in order to optimise future treatment strategie…

Early postoperative recurrence of severe crohnʼs disease, with colonic involvement and associated human cytomegalovirus infection, treated with oral …

2011

2020

Human cytomegalovirus (CMV) remains a major cause of mortality and morbidity in human liver transplant recipients. Anti-CMV therapeutics can be used to prevent or treat CMV in liver transplant recipients, but their toxicity needs to be balanced against the benefits. The choice of prevention strategy (prophylaxis or preemptive treatment) depends on the donor/recipient sero-status but may vary between institutions. We conducted a series of consultations and roundtable discussions with German liver transplant center representatives. Based on 20 out of 22 centers, we herein summarize the current approaches to CMV prevention and treatment in the context of liver transplantation in Germany. In 90…

Modification of the sheet resistance under Ti/Al/Ni/Au Ohmic contacts on AlGaN/GaN heterostructures

2018

This paper reports on the modification of the sheet resistance under Ti/Al/Ni/Au Ohmic contacts on AlGaN/GaN heterostructures, studied by means of Transmission Line Model (TLM) structures, morphological and structural analyses, as well as computer simulations. In particular, the contacts exhibited an Ohmic behaviour after annealing at 800 degrees C, with a specific contact resistance rho(c) = (2.4 +/- 0.2) x 10(-5) Omega cm(2), which was associated to morphological and structural changes of both the metal layer and the interface. Interestingly, TLM analyses gave a value of the sheet resistance under the contact (R-SK = 26.1 +/- 5.0 Omega/rectangle) significantly lower than that measured out…

Nanoscale structural and electrical properties of graphene grown on AlGaN by catalyst-free chemical vapor deposition

2020

The integration of graphene (Gr) with nitride semiconductors is highly interesting for applications in high-power/high-frequency electronics and optoelectronics. In this work, we demonstrated the direct growth of Gr on Al0.5Ga0.5N/sapphire templates by propane (C3H8) chemical vapor deposition (CVD) at temperature of 1350{\deg}C. After optimization of the C3H8 flow rate, a uniform and conformal Gr coverage was achieved, which proved beneficial to prevent degradation of AlGaN morphology. X-ray photoemission spectroscopy (XPS) revealed Ga loss and partial oxidation of Al in the near-surface AlGaN region. Such chemical modification of a 2 nm thick AlGaN surface region was confirmed by cross-sec…