Nitride Semiconductors: The Silicon of the 21st century
Event details
| Date | 29.01.2014 |
| Hour | 10:00 |
| Speaker |
Dr. Elison Matioli, MIT Bio: Elison Matioli received a B.Sc. degree in applied physics and applied mathematics from Ecole Polytechnique (Palaiseau, France) in 2006 and a Ph.D. degree from the Materials Department at the University of California, Santa Barbara (UCSB) in 2010. He is currently a post-doctoral fellow in the Department of Electrical Engineering and Computer Science at the Massachusetts Institute of Technology (MIT). His expertise is in semiconductor and nanostructure growth by metal-organic chemical vapor deposition (MOCVD), device fabrication, coding of advanced numerical models to simulate device properties and in building new device characterization setups. During his thesis, he developed novel nanostructures to significantly enhance the performance of optoelectronic devices, which led to the demonstration of record light-extraction efficiency in LEDs, state-of-the-art performance in nitride-based solar cells and high-brightness polarized light emitters. He received the Outstanding Graduate 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 field of power electronic devices. He has demonstrated nanostructured electronic devices, such as power transistors and Schottky diodes, with large breakdown voltage and up to 4 orders of magnitude lower leakage current (or power losses) than incumbent devices. This work in nanostructured power devices has received critical acclaim and was recognized with the IEEE Electron Devices Society George Smith Award in 2013. |
| Location | |
| Category | Conferences - Seminars |
Nanostructured electronic devices for energy efficiency
The availability of resources beyond hydrocarbons, the ability to meet the world’s future energy needs and the tremendous risk of climate change present critical future challenges. Energy efficiency and renewable energy are the two main pillars of a sustainable future that must be aggressively pursued to address the increasing energy demand while reducing carbon dioxide emissions. Nitride semiconductors have an exceptional set of properties of interest for energy efficiency. Their wide band-gap, large critical electric field and high electron mobility will enable smaller power electronic devices that switch high voltages at higher frequencies, and operate at higher temperatures. This will allow the development of semiconductor-based alternatives to the traditionally bulky and expensive power transformers, switches and converters. Their efficient light emission and tunable direct band-gap covering the visible spectrum offers new possibilities for future photovoltaic cells, light emitting diodes (LEDs) and detectors. Their polarized light emission opens opportunities for new polarized light sources for efficient displays and high-contrast imaging for biological systems.
These properties can be optimally exploited through a judicious nanoscale design of III-nitrides to conceive large-area nanostructured electronic devices that outperform the state of the art. This is the main topic of this talk. First, I will present High Electron Mobility Transistors (HEMTs) with nanostructured gate electrodes that surround the electrons in the transistor channel. This technology largely improved gate control over electrons and reduced off-state leakage current, leading to nanostructured power transistors with normally-off operation, large breakdown voltage of 600 V and 3 orders of magnitude lower leakage current compared to reference planar devices. Later, I apply this concept to improve drastically the performance of Schottky barrier diodes. The combination of these high-efficiency power transistors with fast, low leakage Schottky diodes opens new and exciting possibilities for efficient power systems.
In the second part of the talk, I will present the application of advanced nanostructures for optoelectronic devices. To improve the efficiency of LEDs, I will show a novel configuration of photonic crystals comprising embedded air holes inside the LED structure to form an efficient light diffracting medium. By developing theoretical models and novel techniques to measure the light extraction and dissipation mechanisms, the device structure was optimized, resulting in state of the art light extraction efficiency LEDs of 94% with planar, mass-production compatible fabrication processes. I extend this idea to demonstrate high-brightness polarized LEDs by a judicious design of embedded photonic crystals to preserve polarization and extract light in a directional fashion.
Looking 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.
The availability of resources beyond hydrocarbons, the ability to meet the world’s future energy needs and the tremendous risk of climate change present critical future challenges. Energy efficiency and renewable energy are the two main pillars of a sustainable future that must be aggressively pursued to address the increasing energy demand while reducing carbon dioxide emissions. Nitride semiconductors have an exceptional set of properties of interest for energy efficiency. Their wide band-gap, large critical electric field and high electron mobility will enable smaller power electronic devices that switch high voltages at higher frequencies, and operate at higher temperatures. This will allow the development of semiconductor-based alternatives to the traditionally bulky and expensive power transformers, switches and converters. Their efficient light emission and tunable direct band-gap covering the visible spectrum offers new possibilities for future photovoltaic cells, light emitting diodes (LEDs) and detectors. Their polarized light emission opens opportunities for new polarized light sources for efficient displays and high-contrast imaging for biological systems.
These properties can be optimally exploited through a judicious nanoscale design of III-nitrides to conceive large-area nanostructured electronic devices that outperform the state of the art. This is the main topic of this talk. First, I will present High Electron Mobility Transistors (HEMTs) with nanostructured gate electrodes that surround the electrons in the transistor channel. This technology largely improved gate control over electrons and reduced off-state leakage current, leading to nanostructured power transistors with normally-off operation, large breakdown voltage of 600 V and 3 orders of magnitude lower leakage current compared to reference planar devices. Later, I apply this concept to improve drastically the performance of Schottky barrier diodes. The combination of these high-efficiency power transistors with fast, low leakage Schottky diodes opens new and exciting possibilities for efficient power systems.
In the second part of the talk, I will present the application of advanced nanostructures for optoelectronic devices. To improve the efficiency of LEDs, I will show a novel configuration of photonic crystals comprising embedded air holes inside the LED structure to form an efficient light diffracting medium. By developing theoretical models and novel techniques to measure the light extraction and dissipation mechanisms, the device structure was optimized, resulting in state of the art light extraction efficiency LEDs of 94% with planar, mass-production compatible fabrication processes. I extend this idea to demonstrate high-brightness polarized LEDs by a judicious design of embedded photonic crystals to preserve polarization and extract light in a directional fashion.
Looking 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.
Practical information
- General public
- Free
Organizer
- Prof. Giovanni De Micheli
Contact
- Sylvie Moreau