The E3S Research Mission
The Center for E3S employs a broad research and education approach to revolutionize two major fundamental components of digital information processing systems: the communications logic switch and the short-medium range communication of information between logic elements. These goals are pursued by four distinct research themes. Three themes focus on logic switching (Nanoelectronics, Nanomechanics, and Nanomagnetics), while an optical approach is used for communication of information (Nanophotonics). The Center for E3S addresses these grand challenges by a collaborative approach, involving engineers, chemists, physicists, and materials scientists from five member institutions (University of California at Berkeley, Massachusetts Institute of Technology, Stanford University, University of Texas El Paso, and Florida International University).
The Fundamental Challenge
Binary bits (1’s and 0’s) are the fundamental units used to process and store information in modern electronic devices. Transistors are electrical switches that mediate the two binary states (current ON and current OFF). Integrated circuits, composed of transistors connected by wires (or “interconnects”), are the cornerstone of the modern computer. The performance of integrated circuits has improved as they become smaller. Miniaturization also has led to a decrease in power consumption. However, in the past decade, the semiconductor industry has faced severe challenges by the power density of increasingly complex integrated circuit chips. In addition, recent advancements such as cloud computing, social networking, mobile internet, wireless sensor swarms, and body-centered networks have further accelerated demand for ever increasing functionality from a fixed amount of battery energy.
The Center for E3S was formed based on the recognition that the energy used to manipulate a single bit of information is currently ~100,000 times greater than the theoretical limit. From its inception, the central aim of the Center has thus been to develop an aggressive and disruptive approach to close this gap. To achieve this goal, E3S seeks technological breakthroughs for two fundamental components of digital information processing systems: the communications logic switch (transistor) and the short-medium range communication of information between logic elements.
Conventional transistors suffer from a serious drawback: its conduction is thermally activated. As a consequence, powering voltages of close to 1 Volt are required to provide a good ON/OFF current ratio, even as transistors become smaller and smaller. The wires connecting the transistor, however, could operate with a very good signal-to-noise ratio at voltages as low as 10 milli-Volt. Since energy consumption is proportional to the square of operating voltage, the energy currently used to manipulate a single bit of information is several orders of magnitude greater than needed in an ideal system. Therefore, a more sensitive, lower-voltage switch is needed as the successor to the conventional transistor. In addition to energy for switching, an integrated circuit chip consumes energy for communications between the transistors, through the interconnects. The power consumed by interconnects in a microprocessor chip is substantial, and can reach more than 50 percent of the total consumed power.
Research Goals and Objectives
The research goals of the Center for E3S have been set from fundamental considerations on the minimum energy needed per digital function. Part of the goal is to explore the lowest limits of each experimental approach compared to the fundamental limits, and to elucidate the factors that determine the minimum energy that each approach can reach.
E3S has identified the following critical specifications for a new switch:
- Sensitivity: ~1 milli-Volt/decade, allowing switches with a swing of only few milli-Volts.
- ON/OFF current ratio: 10,000-1,000,000:1
- Current or conductance density (for miniaturization): 1 milli-Siemens/micrometer; i.e. a 1-micrometer device should conduct at ~1 kilo-Ohm in the ON-state.
For optical interconnects to be a low power consumption alternative, the Center’s high level goal is to achieve close to quantum limit detection (20 photons/bit) and communication (~10 atto-Joule/bit).
These goals and objectives are pursued in four distinct, but interrelated research themes: Nanoelectronics (solid-state millivolt switching), Nanomechanics (zero-leakage switching), Nanophotonics (few-photon optical communication), and Nanomagnetics (low-energy fast magnetic switching). Overarching these four research themes is Systems Integration, which checks that the component research outcomes and new scientific device concepts of the Center will actually lead to new energy-efficient system architectures, enabling future ultra-low power information technologies.