Full Understanding of Hot Electrons and Hot/Cold Holes in the Degradation of p-channel Power LDMOS Transistors

Degradation induced by hot-carrier stress is a crucial issue for the reliability of power LDMOS transistors. This is even more true for the p-channel LDMOS in which, unlike the n-channel counterpart, both the majority and minority carriers play a fundamental role on the device reliability. An in-depth study of the microscopic mechanisms induced by hot-carrier stress in new generation BCD integrated p-channel LDMOS is presented in this paper. The effect of the competing electron and hole trapping mechanisms on the on-resistance drift has been thoroughly analyzed. To this purpose, TCAD simulations including the deterministic solution of Boltzmann transport equation and the microscopic degradation mechanisms have been used, to the best of our knowledge, for the first time. The insight gained into the degradation sources and dynamics will provide a relevant basis for future device optimization

Pathological and phylogenetic characterization of Amphibiothecum sp. infection in an isolated amphibian (Lissotriton helveticus) population on the island of Rum (Scotland)

Outbreaks of cutaneous infectious disease in amphibians are increasingly being attributed to an overlooked group of fungal-like pathogens, the Dermocystids. During the last 10 years on the Isle of Rum, Scotland, palmate newts (Lissotriton helveticus) have been reportedly afflicted by unusual skin lesions. Here we present pathological and molecular findings confirming that the pathogen associated with these lesions is a novel organism of the order Dermocystida, and represents the first formally reported, and potentially lethal, case of amphibian Dermocystid infection in the UK. Whilst the gross pathology and the parasite cyst morphology were synonymous to those described in a study from infected L. helveticus in France, we observed a more extreme clinical outcome on Rum involving severe subcutaneous oedema. Phylogenetic topologies supported synonymy between Dermocystid sequences from Rum and France and as well as their distinction from Amphibiocystidium spp. Phylogenetic analysis also suggested that the amphibian-infecting Dermocystids are not monophyletic. We conclude that the L. helveticusinfecting pathogen represents a single, novel species; Amphibiothecum meredithae

The Role of Frequency and Duty Cycle on the Gate Reliability of p-GaN HEMTs

In this letter, we present an extensive analysis on the role of both switching frequency (ranging from 100 kHz to 1 MHz) and duty cycle (from 10% to 90%) on the time-dependent gate breakdown of high electron mobility transistors (HEMTs) with Schottky metal to p-GaN gate. More specifically, results show how the gate lifetime of GaN HEMTs increases by reducing the frequency and the duty cycle of the stressing gate signal (VG). Such behavior is ascribed to the OFF-time, which is responsible to alter the electrostatic potential in the p-GaN layer during the rising phases of VG (from OFF- to ON-state). Findings of this analysis are useful both for further technology improvement and for GaN-based power circuit designers

A Methodology to Account for the Finger Non-Uniformity in Photovoltaic Solar Cell

Abstract In this work we investigate the impact of a non-uniform finger in the front-side metallization on the performance of c-Si solar cells. For this purpose, we propose a methodology based on a mixed-mode simulation approach, which allows evaluating the solar cell properties by performing both numerical device simulations and circuit simulations. The finger roughness profile is modeled by means of Gaussian function. The impact of roughness on the solar cell efficiency is studied as a function of mean finger height, mean finger width and finger resistivity. The proposed methodology has been applied to typical roughness profiles realized with two different metallization techniques, the conventional single screen-printing (SP) and the double screen-printing (DP)

Optimization of Rear Point Contact Geometry by Means of 3-D Numerical Simulation

Abstract In this work three-dimensional (3-D) numerical simulations, validated by the experimental measurements of a reference cell, have been performed to optimize the rear contact geometry of a PERC-type solar cell, featuring a high sheet resistance (140 Ω/sq) phosphorus-doped emitter and a front-side metallization with narrow and highly-conductive electro-plated copper lines (40 μm wide) on lowly resistive Ti contacts. The simulation results show that an optimization of the rear point contact design potentially leads to an efficiency improvement of 0.68%abs compared to the reference cell

Pathological and Phylogenetic characterisation of Amphibiothecum sp. infection in an isolated amphibian (Lissotriton helveticus) population on the island of Rum (Scotland)

Outbreaks of cutaneous infectious disease in amphibians are increasingly being attributed to an overlooked group of fungal-like pathogens, the Dermocystids. During the last 10 years on the Isle of Rum, Scotland, palmate newts (Lissotriton helveticus) have been reportedly afflicted by unusual skin lesions. Here we present pathological and molecular findings confirming that the pathogen associated with these lesions is a novel organism of the order Dermocystida, and represents the first formally reported, and potentially lethal, case of amphibian Dermocystid infection in the UK. Whilst the gross pathology and the parasite cyst morphology were synonymous to those described in a study from infectedL. helveticusin France, we observed a more extreme clinical outcome on Rum involving severe subcutaneous oedema. Phylogenetic topologies supported synonymy between Dermocystid sequences from Rum and France and as well as their distinction fromAmphibiocystidiumspp. Phylogenetic analysis also suggested that the amphibian-infecting Dermocystids are not monophyletic. We conclude that theL. helveticus-infecting pathogen represents a single, novel species;Amphibiothecum meredithae

Cheating on the Edge

We present the results of an individual agent-based model of antibiotic resistance in bacteria. Our model examines antibiotic resistance when two strategies exist: “producers”–who secrete a substance that breaks down antibiotics–and nonproducers (“cheats”) who do not secrete, or carry the machinery associated with secretion. The model allows for populations of up to 10,000, in which bacteria are affected by their nearest neighbors, and we assume cheaters die when there are no producers in their neighborhood. Each of 10,000 slots on our grid (a torus) could be occupied by a producer or a nonproducer, or could (temporarily) be unoccupied. The most surprising and dramatic result we uncovered is that when producers and nonproducers coexist at equilibrium, nonproducers are almost always found on the edges of clusters of producers

Analysis of electron transport in the nano-scaled Si, SOI and III-V MOSFETs: Si/SiO2 interface charges and quantum mechanical effects

The ITRS predicts that the scaling of planar CMOS (Complementary Metal Oxide Semiconductor) technology will continue till the 22 nm technology node [1] and a possible extension beyond is appealing [2]. In this work, we investigate the effect of electron confinement [3] in nanoscaled transistor channels of 25 nm surface channel Si and 32 nm SOI (Silicon on Insulator) and 15 nm IF (Implant Free) III-V MOSFETs using a self-consistent solution of 1 D Poisson - Schrödinger equation [4,5]. For simulat ion and development with accuracy of nano-scaled of 25 nm gate length Si MOSFET (Metal Oxide Semiconductor Field Effect Transistor), 32 nm SOI Implant Free (IF) MOSFET, and 15nm Implant Free III-V MOSFET transistors, we investigated the bandstructure and quantum confinement effects occurring near the oxide-semiconductor interface inmetal-Oxide-Semiconductor (MOS) structure of Si MOSFET device. These investigation have been carried out using a selfconsistent solution of 1D Poisson-Schrödinger equation across the channel of conventional Si / SOI / III-V MOSFET Transistors. To solve self-consistently 1D Poisson-Schrödinger equations across the channel of a conventional Si, SOI, and an Implant Free III-V MOSFETs to determine the conduction and valence band profiles, electron density, electron sheet density, eigenstate and eigenfunctions in these structures. We present the simulat ion results of conduction band profile, electron density (classical and quantum mechanical), eigenstate and eigenfunctions for Si, SOI and III-V MOSFET structures at two different bias voltages of 0.5 V and 1.0 V. For comparison, we calculate the electron sheet density (quantum mechanically) as a function of the applied gate voltages

Cheaters allow cooperators to prosper

Cooperation based on the production of costly common goods is observed throughout nature. This is puzzling, as cooperation is vulnerable to exploitation by defectors which enjoy a fitness advantage by consuming the common good without contributing fairly. Depletion of the common good can lead to population collapse and the destruction of cooperation. However, population collapse implies small population size, which, in a structured population, is known to favor cooperation. This happens because small population size increases variability in cooperator frequency across different locations. Since individuals in cooperator-dominated locations (which are most likely cooperators) will grow more than those in defector-dominated locations (which are most likely defectors), cooperators can outgrow defectors globally despite defectors outgrowing cooperators in each location. This raises the possibility that defectors can lead to conditions that sometimes rescue cooperation from defector-induced destruction. We demonstrate multiple mechanisms through which this can occur, using an individual-based approach to model stochastic birth, death, migration, and mutation events. First, during defector-induced population collapse, defectors occasionally go extinct before cooperators by chance, which allows cooperators to grow. Second, empty locations, either preexisting or created by defector-induced population extinction, can favor cooperation because they allow cooperator but not defector migrants to grow. These factors lead to the counterintuitive result that the initial presence of defectors sometimes allows better survival of cooperation compared to when defectors are initially absent. Finally, we find that resource limitation, inducible by defectors, can select for mutations adaptive to resource limitation. When these mutations are initially present at low levels or continuously generated at a moderate rate, they can favor cooperation by further reducing local population size. We predict that in a structured population, small population sizes precipitated by defectors provide a "built-in" mechanism for the persistence of cooperation