You are invited to attend a lecture

New Frontiers in Band-Gap Engineering: Stretching the Limits of Quantum Transport

By:

Dr. Asaf Albo

Research Laboratory of Electronics, Massachusetts Institute of Technology, USA

Abstract

The extreme precision in semiconductor materials growth together with their high quality allows to extend band-gap engineering to control not only the band gap across a device but also the electron dynamics and scattering processes. One of the greatest achievements using this approach is terahertz  quantum cascade lasers (THz-QCLs) founded on designed electron dynamics in less than handful of subbands. As a demonstrative case study for this capability, I will review my efforts to untangle the complexity of the temperature driven electron transport in THz-QCLs towards extending their operation to room temperature (). This study has led to the experimental demonstration of negative differential resistance at room temperature in THz-QCL structures. This is a strong evidence for the possibility to achieve lasing at room temperature.  The study points also to a future direction in quantum engineering that is to control and manipulate generated heat and carriers’ temperature for the benefit of the device and for the realization of novel device concepts.

A further example of novel band gap engineering is the expansion in design flexibility of devices through the synthesis of novel semiconductor materials.  The incorporation of additive atoms to conventional semiconductor alloys is suggested as an efficient strategy to extend their functionality. As an example for this approach, I will review my contributions on MOCVD growth of mixed-anion III-V-N (dilute-nitrides) alloys and demonstrate the increased flexibility that was achieved in designing novel quantum structures and devices.

I will conclude with presenting the high potential of related novel III-nitride (III-N) materials and quantum structures to solve key technological challenges in optoelectronics.

On Thursday, January 26, 2017, 15:00

Room 011, Kitot building

School of Mechanical Engineering Seminar
Wednesday, March 22, 2017 at 14:00
Wolfson Building of Mechanical Engineering, Room 206

A deeper look at the role of oxygen on bio-kinetics in wastewater reuse systems

Liron Friedman

PhD Student of Prof. Hadas Mamane and Prof. Dror Avisar

Wastewater reuse by biological tertiary treatment of secondary effluent is gaining interest as a promising sustainable solution in water-scarce environments worldwide. Media attached systems, as high rate biofiltration and Soil Aquifer Treatment (SAT), are well-practiced processes, especially in Israel, for producing high quality reusable water to support food production. During the flow of the secondary effluent through the media, the attached microbiota utilizes and removes residual organics and nitrogen by various metabolic pathways and rates determined by environmental conditions. Oxygen availability is a key parameter for system design and optimized performance. However, microbiota structure-function (bio-kinetics) links in such engineered systems have not been elucidated similarly to other engineered processes for biological wastewater treatment. In this seminar, two case studies will be presented: (1) the role of oxygen in the tertiary treatment: a pilot biofiltration research conducted at the SHAFDAN Wastewater treatment plant and (2) lab scale research simulated SAT conducted at Columbia University, NY, focusing on new methodologies using next generation sequencing, the associated substrate transformation and modeling.

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