Research

SUMMARY

Historically, integrated electronics has focused primarily on scaling the dimension of silicon-based devices. Until recently, very little has changed in the materials and design of these silicon devices. Alternative materials and device structures are now required to continue device scaling. Furthermore, as silicon technology approaches its limits, entirely new materials (e.g. graphene) and computational paradigms (e.g. neuro-inspired) will be critical to continuing the acceleration of the rate of technical change. Although increasing computational speed will likely continue for the foreseeable future, new paradigms are becoming as or more important. The concept of functional electronic materials where new functionality (e.g. chemical or biological sensing) is performed on a silicon platform is an increasingly important paradigm. One theme that pervades these seemingly disparate emerging technologies is that the electronic properties of the devices are extremely sensitive to the structural and physical properties of their constituent materials. Our group pursues broad-based, cross-disciplinary research that spans the development and fundamental understanding of electronic materials and devices.

 

Graphene

Graphene, a monolayer of carbon atoms arranged in a hexagonal lattice, has very unique electronic properties. For example, it has been theoretically predicted that bilayers of graphene can sustain a Bose-Einstein condensate at room temperature which could be used as a novel low-power device: the Bilayer pseudo-Spin Field Effect Transistors (BiSFET). Whether one is considering graphene for a BiSFET, a tunnel transistor, for RF applications, for sensors, or some other device, realization will require a controlled integration of graphene into a device structure with multiple material components of metals and insulators. We are exploring a variety of issues related to the impact of these materials and associated interfaces on the final electronic properties of graphene devices.

 

 

Neuro-inspired Materials, Devices, and Architectures

Future computer systems will not rely solely on digital processing of inputs from well-defined data sets. They will also be required to perform various computational tasks using large sets of ill-defined information from the complex environment around them. The most efficient processor of this type of information known today is the human brain. Using a large number of primitive elements (~1010 neurons in the neocortex) with high parallel connectivity (each neuron has ~104 synapses), brains have the remarkable ability to recognize and classify patterns, predict outcomes, and learn from and adapt to incredibly diverse sets of problems. We are exploring low temperature processed materials to implement neuromorphic devices and circuits which are consistent with the use of flexible substrates or in 3-D applications where the complete neuromorphic circuit is integrated with a CMOS core.

 

 

Bio-sensors

For over 30 years, field effect transistors (FETs) have been used as ion sensors. Recently, functionalized silicon nanowires have been introduced into sensor architecture to detect a variety of species including proteins, DNA, and even single viruses. The application of semiconductors to a biological environment introduces new challenges. For instance, in addition to specific device designs, careful consideration must be given to the properties of the liquid media and its interactions with the FET. This is paramount not only to the resolution of the “true” sensing signal from that of other factors but also to enhancing manufacturability and reliability of these devices. Our work focuses on material, surface and device issues related to semiconductor-based chemical and biological sensors.

 

 


High-k Dielectrics for III-V CMOS and Memories

High-k dielectrics such as HfO2 and Al2O3 are being considered for a variety of applications including as a gate dielectric for III-V transistors, as a dielectric in floating gate memories, and as the dielectric for resistive change memories. We are exploring a variety of issues related to how the materials properties of high-k dielectrics and their interfaces affect the performance of electronic devices
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