Tomas Palacios´Group @ MIT

Our research interest is in the field of advanced electronic devices based on compound semiconductors and nanotechnology. By “advanced”, we understand the use of radically new concepts and a multidisciplinary approach to both improve already existing devices and to fabricate completely new semiconductor-based micro- and nano-systems. These devices will help the introduction of Electrical Engineering in numerous new fields, including its next frontier, its interaction with biological systems. Electrical Engineering is at a crossroads. In the last half century, electronics has driven the development of information technology that has completely changed our society. This development has been possible mainly due to the integration of devices like transistors, light emitting diodes, lasers and detectors with advanced design methodologies and parallelism. In spite of the wide breadth of these devices, all of them are based on few key concepts of semiconductor physics: channel modulation by field effect, depletion regions, carrier recombination, drift-diffusion transport, etc. Our group firmly believes that after more than 50 years of semiconductor technology development, if we want semiconductor devices to keep changing the society as they have done in the past century, it is not longer enough an evolutionary approach based on these concepts in combination with improved technology and better material quality. We need to adopt a multidisciplinary effort that uses the tools provided by areas like nanotechnology and biotechnology in conjunction with standard semiconductor physics, processing and material growth. Only with this approach will radical improvements in performance – as well as new devices – come out to push information technology well into the 21^st century.
Since 1998, we have been involved with various micro- and opto-electronic devices fabricated in different semiconductor material systems. Out of all of these systems, nitride-based semiconductors have a unique combination of properties that make them especially suitable for many of the new challenges and applications of the 21st century.This material system is characterized by a wide range of very interesting properties, which make it the most complete semiconductor family. Some of these properties are: a direct bandgap tunable from 6.2 eV (AlN) down to 0.6 eV (InN), piezoelectricity, polarization, large breakdown voltage, biocompatibility, high chemical and thermal stability, etc. Moreover, even superconductivity and ferromagnetism have been proposed by some researchers. This vast array of properties make these semiconductors ideal for many applications, including LEDs and lasers, photodetectors, transistores, piezoelectric filters, biosensors, etc.
In our group, we combine the amazing properties of nitrides semiconductor and graphene to fabricate new electronic devices with unique functionality. We are especially interested in four main research areas:
GaN transistors are the primary option for high performance power amplifiers at microwave frequencies (1-10 GHz). In the last few years, we have helped to demonstrate that these devices also shown outstanding performance at mm-wave frequencies (30-40 GHz) with a x10 more power than in other competing technologies. The next big challenge is to show that this material system is the best option even for sub-mm wave transistors (f>60 GHz). Multiple applications ranging from ultra high speed digital logic to new imaging concepts await at frequencies above 200 GHz and nitrides could be the best option for them.	Power and logic at mm-wave frequencies
Society is demanding new energy sources and more compact and efficient electrical systems. Nitrides have traditionally helped to save energy by allowing the fabrication of energy efficient light sources like while LEDs. It is time now to uncover the huge impact that nitrides will also have in energy saving from the electronics side. Each day, nitrides are becoming more and more important in this field with a large array of applications: new solar cells, hydrogen generation for fuel cells, compact power adaptors and conversion systems, etc. The large tunable bandgap of nitride alloys in combination with the great design flexibility given by polarization engineering will be critical to revolutionize this field.	Energy saving and conversion
Graphene is a zero bandgap semiconductor with an electron and hole mobility above 100,000 cm2/V.s. In addition, being one-atom-thick it is the thinnest material in the world and also, the strongest. Our group, in close collaboration with physicists, material scientists and chemists, is developing new electronic devices that take advantage of the unique properties of this amazing material. Some examples of our recent developments include, RF frequency multipliers, mixers, PSK modulators and the first graphene radio demodulator.	Graphene-based RF Electronics
The outstanding properties of GaN and graphene make these materials ideal for new biosensor devices. They are biocompatible and the combination of their excellent electronic, optoelectronics and piezoelectric properties allows the fabrication of completely new biosensor devices with significantly improved performance with respect to standard devices. These devices are expected to have a unique combination of both very high specificity and sensitivity as well as a robustness and chemical stability not present in any competing Si device.	New biosensors and actuators
In all these research areas, we try to cover all the major steps of device engineering. In this way, our students have the opportunity to learn about all these different steps. For example, from their work in the cleanroom they learn a lot about semiconductor technology; the use of custom-made and commercial simulation packages like ADS or ATLAS gives them a deep understanding about the working principles of these devices; finally, they also have access to state-of-the-art DC and high frequency measurement labs to test the devices and compare the results with the simulations. We try to combine the development of state-of-the-art devices with a broad education in all the important fields of device engineering. We also put an important emphasis on collaborations with companies and universities in the US and abroad. This is, we believe, the best way to compete in the global environment in which we are today.If you would like to get additional information about any of the topics mentioned above, please do not hesitate to contact us at .