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SUMMARY:Nitride Semiconductors: The Silicon of the 21st century
DTSTART:20140129T100000
DTSTAMP:20260916T052753Z
UID:da99e0b8c8089611692833ee526edca73fd88d36bae3ee41b8b8ce50
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. Elison Matioli\, MIT\nBio: Elison Matioli received a B.Sc.
  degree in applied physics and applied mathematics from Ecole Polytechniqu
 e (Palaiseau\, France) in 2006 and a Ph.D. degree from the Materials Depar
 tment at the University of California\, Santa Barbara (UCSB) in 2010. He i
 s currently a post-doctoral fellow in the Department of Electrical Enginee
 ring and Computer Science at the Massachusetts Institute of Technology (MI
 T).\nHis expertise is in semiconductor and nanostructure growth by metal-o
 rganic chemical vapor deposition (MOCVD)\, device fabrication\, coding of 
 advanced numerical models to simulate device properties and in building ne
 w device characterization setups. During his thesis\, he developed novel n
 anostructures to significantly enhance the performance of optoelectronic d
 evices\, which led to the demonstration of record light-extraction efficie
 ncy in LEDs\, state-of-the-art performance in nitride-based solar cells an
 d high-brightness polarized light emitters. He received the Outstanding Gr
 aduate Student Award for his Ph.D. work at UCSB. At MIT\, he has extended 
 his ideas from advanced optics developed at UCSB to the very different fie
 ld of power electronic devices. He has demonstrated nanostructured electro
 nic devices\, such as power transistors and Schottky diodes\, with large b
 reakdown voltage and up to 4 orders of magnitude lower leakage current (or
  power losses) than incumbent devices. This work in nanostructured power d
 evices has received critical acclaim and was recognized with the IEEE Elec
 tron Devices Society George Smith Award in 2013.\nNanostructured electroni
 c devices for energy efficiency\nThe availability of resources beyond hydr
 ocarbons\, the ability to meet the world’s future energy needs and the t
 remendous risk of climate change present critical future challenges. Energ
 y efficiency and renewable energy are the two main pillars of a sustainabl
 e future that must be aggressively pursued to address the increasing energ
 y demand while reducing carbon dioxide emissions. Nitride semiconductors h
 ave an exceptional set of properties of interest for energy efficiency. Th
 eir wide band-gap\, large critical electric field and high electron mobili
 ty will enable smaller power electronic devices that switch high voltages 
 at higher frequencies\, and operate at higher temperatures. This will allo
 w the development of semiconductor-based alternatives to the traditionally
  bulky and expensive power transformers\, switches and converters. Their e
 fficient light emission and tunable direct band-gap covering the visible s
 pectrum offers new possibilities for future photovoltaic cells\, light emi
 tting diodes (LEDs) and detectors. Their polarized light emission opens op
 portunities for new polarized light sources for efficient displays and hig
 h-contrast imaging for biological systems.\nThese properties can be optima
 lly exploited through a judicious nanoscale design of III-nitrides to conc
 eive large-area nanostructured electronic devices that outperform the stat
 e of the art. This is the main topic of this talk. First\, I will present 
 High Electron Mobility Transistors (HEMTs) with nanostructured gate electr
 odes that surround the electrons in the transistor channel. This technolog
 y largely improved gate control over electrons and reduced off-state leaka
 ge current\, leading to nanostructured power transistors with normally-off
  operation\, large breakdown voltage of 600 V and 3 orders of magnitude lo
 wer leakage current compared to reference planar devices. Later\, I apply 
 this concept to improve drastically the performance of Schottky barrier di
 odes. The combination of these high-efficiency power transistors with fast
 \, low leakage Schottky diodes opens new and exciting possibilities for ef
 ficient power systems.\nIn the second part of the talk\, I will present th
 e application of advanced nanostructures for optoelectronic devices. To im
 prove the efficiency of LEDs\, I will show a novel configuration of photon
 ic crystals comprising embedded air holes inside the LED structure to form
  an efficient light diffracting medium. By developing theoretical models a
 nd novel techniques to measure the light extraction and dissipation mechan
 isms\, the device structure was optimized\, resulting in state of the art 
 light extraction efficiency LEDs of 94% with planar\, mass-production comp
 atible fabrication processes. I extend this idea to demonstrate high-brigh
 tness polarized LEDs by a judicious design of embedded photonic crystals t
 o preserve polarization and extract light in a directional fashion.\nLooki
 ng towards the future\, I will discuss a broader vision to further unleash
  the full potential of nitride semiconductors as the main player in energy
  efficiency in the 21st century.
LOCATION:ME B1 B10 http://plan.epfl.ch/?lang=en&room=MEB1B10
STATUS:CONFIRMED
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