On the leverage of high-fT transistors foradvanced high-speed bipolar circuits

A detailed study on the leverage of high-f_T transistors for advanced high-speed bipolar circuit applications is presented. It is shown that for the standard ECL (emitter-coupled logic) circuit, the leverage of high f_T is limited by the passive resistors (emitter-follower resistor and collector load resistor) and wire delay, especially in the low-power regime. For the standard NTL (nonthreshold logic) circuit, the leverage is higher due to its front-end configuration and lower power supply value. As the passive resistors are decoupled from the delay path in various advanced circuits utilizing active-pull-down schemes, the leverage of high F_T becomes more significant     

Si/SiGe epitaxial-base transistors. I. Materials, physics, andcircuits

A detailed review of SiGe epitaxial base technology is presented, which chronicles the progression of research from materials deposition through device and integration demonstrations, culminating in the first SiGe integrated circuit application. In part I of this paper, the requirements and processes for high-quality SiGe film preparation are discussed, with emphasis on fundamental principles. A detailed overview of SiGe HBT device design and implications for circuit applications is then presented     

GeneMCL in microarray analysis

Accurately and reliably identifying the actual number of clusters present with a dataset of gene expression profiles, when no additional information on cluster structure is available, is a problem addressed by few algorithms. GeneMCL transforms microarray analysis data into a graph consisting of nodes connected by edges, where the nodes represent genes, and the edges represent the similarity in expression of those genes, as given by a proximity measurement. This measurement is taken to be the Pearson correlation coefficient combined with a local non-linear rescaling step. The resulting graph is input to the Markov Cluster (MCL) algorithm, which is an elegant, deterministic, non-specific and scalable method, which models stochastic flow through the graph. The algorithm is inherently affected by any cluster structure present, and rapidly decomposes a graph into cohesive clusters. The potential of the GeneMCL algorithm is demonstrated with a 5,730 gene subset (IGS) of the Van't Veer breast cancer database, for which the clusterings are shown to reflect underlying biological mechanisms.     

High-mobility modulation-doped SiGe-channel p-MOSFETs

A novel subsurface SiGe-channel p-MOSFET is demonstrated in which modulation doping is used to control the threshold voltage without degrading the channel mobility. A novel device design consisting of a graded SiGe channel, an n⁺ polysilicon gate, and p⁺ modulation doping is used. A boron-doped layer is located underneath the graded and undoped SiGe channel to minimize process sensitivity and maximize transconductance. Low-field hole mobilities of 220 cm²/V-s at 300 K and 980 cm²/V-s at 82 K were achieved in functional submicrometer p-MOSFETs     

On the profile design and optimization of epitaxial Si- andSiGe-base bipolar technology for 77 K applications. II. Circuitperformance issues

For pt.I see ibid., vol.40, no.3, p.525-41 (1993). The circuit performance issues associated with optimizing epitaxial Si- and SiGe-base bipolar technology for the liquid-nitrogen temperature environment are examined in detail. It is conclusively demonstrated that the notion that silicon-based bipolar circuits perform poorly at low temperatures is untrue. Transistor frequency response is examined both theoretically and experimentally, with particular attention given to the differences between SiGe and Si devices as a function of temperature. ECL and NTL ring oscillator circuits were fabricated for each of the four profiles described in pt.I. The minimum ECL gate delay for a SiGe base is essentially unchanged from its room-temperature value. ASTAP models were used to explore circuit operation under typical wire loading. The results indicate that epitaxial-base bipolar technology offers significant leverage for future cryogenic applications     

Synthesis of new allenic prostanoids

New allenic prostanoids 5c, d, 7,9c, and 15b have been prepared by total synthesis. In each case a cuprate-propargylic acetate reaction was used as the key step.     

Modelling effects of geoengineering options in response to climate change and global warming: Implications for coral reefs

Climate change will have serious effects on the planet and on its ecosystems. Currently, mitigation efforts are proving ineffectual in reducing anthropogenic CO₂ emissions. Coral reefs are the most sensitive ecosystems on the planet to climate change, and here we review modelling a number of geoengineering options, and their potential influence on coral reefs. There are two categories of geoengineering, shortwave solar radiation management and longwave carbon dioxide removal. The first set of techniques only reduce some, but not all, effects of climate change, while possibly creating other problems. They also do not affect CO₂ levels and therefore fail to address the wider effects of rising CO₂, including ocean acidification, important for coral reefs. Solar radiation is important to coral growth and survival, and solar radiation management is not in general appropriate for this ecosystem. Longwave carbon dioxide removal techniques address the root cause of climate change, rising CO₂ concentrations, they have relatively low uncertainties and risks. They are worthy of further research and potential implementation, particularly carbon capture and storage, biochar, and afforestation methods, alongside increased mitigation of atmospheric CO₂ concentrations.