Imperial College London

DrKristelFobelets

Faculty of EngineeringDepartment of Electrical and Electronic Engineering

Reader in Microelectronics Engineering
 
 
 
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Contact

 

+44 (0)20 7594 6236k.fobelets Website

 
 
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Assistant

 

Mrs Jay Sahote +44 (0)20 7594 6215

 
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Location

 

714Electrical EngineeringSouth Kensington Campus

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Summary

 

Overview

My approach to the exploration of science and technology in semiconductors has always been to cover all aspects of research, including material characterization, device design, micro- and nano- fabrication and electrical characterization.

I invented the Screen-Grid Field Effect Transistor. This is a FET with a novel gating structure that incorporates nanoholes. This gate geometry, not really CMOS compatible, boosts both digital as well as analogue performance and can also be exploited for biosensing. I have proposed its use as an active Coulter counter. I and my PhD student won the best invited paper award at the WOFE 2007 workshop for this work. The work was carried out in collaboration with Prof. J.E. Velazquez-Perez from the University of Salamanca in Spain. 

I used low frequency noise measurements for analyzing material problems in spintronics devices. This work was a result of a collaboration with RPI in Troy, USA and IMEC in Belgium. We received the best paper award in device reliability at the MIEL 2008 conference for using this technique. Using low frequency noise is also a powerful tool to sense small variations at the surface of the device and I have exploited this in nanowire arrays for gas sensing.

I designed the Y-branch finFET in 2010. In this FET the drain is split in two and increases the functionality of the FET. Simulations of the Y-branch finFET show an increase in speed performance and a decrease in manufacturability complexity compared to the 2 parallel connected finFETs.

My research on thermoelectric power generation started recently. I explore the use of silicon nanowire arrays attached to bulk for thermoelectric power generation. My research team had some breakthroughs recently with the use of SiGe and spin-on-doping, obtaining ~10 μW for a temperature difference of only 20°C. This is approximately 40% more than that generated by the bulk.

Vision

Nanotechnology is the current new revolution. It is of a different kind than the industrial or the digital revolution because of its highly multidisciplinary character. Nanotechnology is now embraced in semiconductor technology rather than shunned, using quantum effects to boost performance. For sensing, it has opened new doors, since the active part of devices has gone down to a scale of bacteria and viruses. Thus interactions between them can lead to novel detectors. Combinations of nanoparticles in different materials e.g. organic and inorganic compounds can lead to material improvements that are larger than the sum of their parts for electrical, optical and mechanical applications.

One of my key interests at the moment is the exploration of nanotechnology within the current global energy crisis. It is not sufficient to deal with researching alternative energy generation techniques but it also needs to be done in an economic way and using sustainanble materials and processes. Therefore I explore the use of silicon nanowires - a "cheap" semicondcutor - for energy generation and storage. The technique used does not involve expensive technology but is based on simple chemical processes.

For instance, nanoscale semiconductors and metals in combination with polymers open the way for low-cost photovoltaics. Since nanoscale dimensions have resolved the Wiedemans-Franz bottleneck in thermoelectric energy generation, we can increase efficiencies in materials where none existed before, e.g. Si. Using Si nanowires and solid polyelectrolytes can lead to supercapacitors for energy storage and doing everything in silion leads to smart integrated circuits. This opens a future in which personal energy generation can be combined with portable electronics such as iphones, medical devices and many more.

Collaborators

Dr. S. Roumyantsev, Ioffe Institute, Russia, low frequency noise measurements, 2006

Prof. J. Lusakowski, University of Warsaw, Poland, Terahertz applications, 2010

Dr. R. Loo, IMEC, Belgium, Si/SiGe growth, 2010

Prof. M. Shur, Rensellaer Polytechnic Institute, Troy, USA, Solid State Devices, 2006

Dr. D. Coquillat, University of Montpellier, France, Terahertz spectroscopy, 2010

Prof. J. E. Velazquez-Perez, University of Salamanca, Spain, Modelling and simulation of semiconductor devices, 2001

Guest Lectures

Invited Talk - C. Li , B. Cheng, Q. Wang and K. Fobelets, “Si based nanowires for thermoelectric application”, The 2013 EMN East Meeting, Beijing, China, 2013

Invited Talk - C. Li , B. Cheng, Q. Wang and K. Fobelets, “Conductance modulation of Si nanowire array”, IUMRS-ICAM International conference on advanced materials, Qingdao, China, 2013

Invited talkChuanbo Li, Kristel Fobelets, Zahid Durrani, and Q.M. WangSi/Ge for clean energy applications, International Workshop on Group IV Nano Materials & Advanced Devices Applications, Nanjing, 2011

Research Student Supervision

Rahman,T, Si nanowire arrays for photovoltaics

Xu,B, Si/SiGe nanowire arrays for thermoelectric power generation

Yuk,H-S, Fabrication of SiGe-on-insulator for strained-Si heterostructure technologies

Gaspari,V, Temperature effects in SiGe Modulation Doped Field Effect Transistors

Vilches,A, SiGe HFETs micropower circuits

Li,SM, Alternative approaches to Silicon-Germanium Modulation Doped Field Effect Transistor processing

Ferguson,RS, Characterisation of Silicon-Germanium Heterostuctures by Kelvin Probe Force Microscopy

Jeamsaksiri,W, Modelling and simulation of SiGe n-channel HFETs for low power applications

Ding,PW, Development of Screen-Grid FET

Shadrokhsikary,Y, Digital benchmarking of the SGFET