Theoretical analysis and experimental study of the space-charge-screening effect in uni-traveling-carrier photodiode

A new optimized structure of an UTC (uni-traveling-carrier) photodiode is developed and epitaxied by metal-organic chemical vapor deposition. We fabricated a UTC photodiode of 30 mu m in diameter. Theoretical simulation based on drift-diffusion model was used to analyze the space-charge-screening effect in UTC photodiode primarily in two aspects: the carrier concentrations and the space electric field. The simulation results were generally in agreement with the experimental data.

A new phototransistor with uni-travelling-carrier and optically gradual coupling properties

Based on appropriate combination of different band-gap InGaAsP, a new edge-coupled two-terminal double heterojunction phototransistor (ECTT-DHPT) was designed and fabricated, which is double heterojunction, free-aluminium, and works under uni-travelling-carrier mode and optically gradual coupling mode. This device is fully compatible with monolithic micro-wave integrated circuits (MMIC) and heterojunction bipolar transistor (HBT) in material and process. The DC characteristics reveal that the new ECTT-DHPT can perform good optoelectronic mix operation and linear amplification operation by optically biased at two appropriate value respectively. Responsivity of more than 52 A/W and dark current of 70 nA (when V-EC = 1 V) were obtained.

High-performance evanescently-coupled uni-traveling-carrier photodiodes

A new evanescently-coupled uni-traveling-carrier photodiode (EC-UTC PD) based on a multimode diluted waveguide (MDW) structure is fabricated, analysed and characterized. Optical and electrical characteristics of the device are investigated. The excellent characteristics are demonstrated such as a responsivity of 0.36 A/W, a bandwidth of 11.5 GHz and a small-signal 1-dB compression current greater than 18 mA at 10 GHz. The saturation current is significantly improved compared with those of similar evanescently-coupled pin photodiodes. The radio frequency (RF) bandwidth can be further improved by eliminating RF losses induced by the cables, the probe and the bias tee between the photodiode and the spectrum analyzer.

Fabrication and Investigation of High Efficiency Evanescently Coupled Uni-Traveling Carrier Photodiodes

In this paper, an evanescently coupled uni-traveling carrier photodiodes (EC-UTC-PDs) have been fabricated and investigated, which can benefit from the incorporation of a multimode diluted waveguide of appropriate length with experiment-simulation comparison. A high responsibvity of 0.68 A/W at 1.55-mu m without an anti-reflection coating, -1 dB compression current of more than 19 mA, and a large -1 dB vertical alignment tolerance of 2.2 mu m were achieved.

Design and Characterization of Evanescently Coupled Uni-Traveling Carrier Photodiodes with a Multimode Diluted Waveguide Structure

A new evanescently coupled uni-traveling carrier photodiode (EC-UTC-PD) is designed, fabricated and characterized, which incorporates a multimode diluted waveguide structure and UTC active waveguide structure together. A high responsivity of 0.68A/W at 1.55-mu m without an anti-reflection coating, a linear photocurrent responsivity of more than 21 mA, and a large-1 dB vertical alignment tolerance of 2.5 mu m are achieved.

Monolithic optical gates based on integration of evanescently-coupled uni-traveling-carrier photodiodes and electroabsorption modulators

We report on chip-scale optical gates based on the integration of evanescent waveguide unitraveling-carrier photodiodes (EC-UTC-PDs) and intra-step quantum well electroabsorption modulators (IQW-EAMs) on n-InP substrates. These devices exhibit simultaneously 2.1 GHz and -16.2 dB RF-gain at 21 GHz with a 450 Omega thin-film resistor and a bypass capacitor integrated on a chip.

P2BES. Desarrollo de proyectos integrales orientados al desarrollo temprano de productos. Caso del “Elder Assistant”

La enseñanza utilizando proyectos es una metodología activa de aprendizaje de gran eficiencia. En la Universidad Europea se ha lanzado con éxito la implantación de proyectos integrales que abarcan varias asignaturas de un mismo curso como una herramienta poderosa de enseñanza. Uno de los posibles pasos futuros de esta metodología es que estos proyectos sirvan para el desarrollo temprano de productos o de prototipos, lo que podríamos llamar Product and Project Based Engineering School o P2BES. En este artículo se narran las experiencias obtenidas en el caso de un prototipo concreto, un sistema básico de asistencia a ancianos llamado “Elder Assistant”. En este artículo también se han identificado un conjunto de aspectos a evaluar sobre el rol del profesor en este tipo de proyectos.

Contribución al estudio de la cadena agroalimentaria de la carne de la liebre europea en al Argentina

p.31-40

Harpidium rutilans (FIot.) Koerb. una especie rara de la flora Iiquénica europea

Se divulga la presencia de Harpidium rutilans en la Península Ibérica, presentando la distribución mundial conocida hasta el momento de esta interesante especie. Se incorpora unadescripción morfológica detallada, así como datos taxonómicos y geobotánicos.

Reception and schooling of children in schools in Catalonia: Beyond Educational Welcome Facilities

The ways of incorporating newcoming students into schools and colleges have been at the center of debate in most OECD countries in recent years. In Spain, the set of measures developed for the reception of immigrant pupils in different Autonomous Communities has also been the subject of specific research, pointing out the similarities and contradictions between pedagogic discourses and school practices. This article takes into account these considerations and presents the reflections from the results of research on the Educational Welcome Facilities (and specifically the EBE) conducted during the school years 2008-2010. This device was created in Catalonia to attend newcomers before enrolling them in the school. It was a pilot project which took place in Vic and Reus for two consecutive years. The research of the EBE has enabled us to explain the relationship between educational assessment that schools made about this facility and reception processes that schools were implementing. The conclusions that emerge from this analysis allowed us to establish relationships between educational host practices of the seven centers analyzed with three different conceptual and educational frameworks of reception.

Los primeros pasos en el escorzo de la figura humana. "Un análisis desde la geometría"

A través de un recorrido histórico centrado en el Renacimiento, se exponen las aportaciones más significativas de teóricos y artistas en la evolución del escorzo de la figura humana desde un punto de vista geométrico. Los artistas que con sus dibujos y escritos ayudaban a otros en el aprendizaje de la representación, se apresuraron a incluir el estudio del escorzo en sus tratados, buscando métodos que facilitaran su dibujo sobre cualquier soporte y en cualquier posición en el espacio. En este artículo se analizan y enlazan los trazados propuestos por los estudiosos de la geometría, con las obras de arte que reflejan importantes avances en este sentido. Soportes como el lienzo, el muro o la bóveda, presentan al pintor superficies diferentes de trabajo y en distintas posiciones en el espacio. La figura humana, protagonista en la escena, tendrá que adaptarse a ellos para ser contemplada desde unos espacios arquitectónicos cada vez más amplios y con más posibilidades. Fue necesario dominar la perspectiva en la pintura, y muy particularmente en la mural, para ofrecer composiciones cada día más ambiciosas y sorprendentes.