Integrated logic circuits using single-atom transistors

Abstract

Scaling down the size of computing circuits is about to reach the limitations imposed by the discrete atomic structure of matter. Reducing the power requirements and thereby dissipation of integrated circuits is also essential. New paradigms are needed to sustain the rate of progress that society has become used to. Single-atom transistors, SATs, cascaded in a circuit are proposed as a promising route that is compatible with existing technology. We demonstrate the use of quantum degrees of freedom to perform logic operations in a complementary-metal-oxide-semiconductor device. Each SAT performs multilevel logic by electrically addressing the electronic states of a dopant atom. A single electron transistor decodes the physical multivalued output into the conventional binary output. A robust scalable circuit of two concatenated full adders is reported, where by utilizing charge and quantum degrees of freedom, the functionality of the transistor is pushed far beyond that of a simple switch.cascading full adder | CMOS technology | energy and charge quantization I n digital logic circuits, binary information is encoded by monitoring the current, on vs. off, through a transistor that serves as a switch. This concept has been extremely effectively scaled over the last decades and led to the exceptionally dense and low cost integrated circuits that we use today. Decreasing the physical size of the component transistors has largely enabled the miniaturization. The reduction in the size of conventional transistors will shortly face the barrier that on the subnano length scale matter is discrete. The atomistic nature of matter leads to variability in device characteristics, which is the major problem in device downscaling. As we approach the physical limits of two-dimensional circuits essentially new paradigms are needed to sustain the rate of progress that our society has become used to. Here we utilize the discrete nature of matter at the atomic scale to offer a viable solution. Deterministic doping (1-3) emerges as a technique that overcomes variability problems (4). Furthermore, single atom doping allows for device functionality that exceeds that of a simple switch. This functionality of single-atom transistors, SATs, is robust due to the strong natural confinement of the Coulomb potential of the dopant. We connect the basic units, the SATs, with gain thereby allowing for a scalable circuit. It is because of the nature of SATs that our innovative Si device and experimental design can significantly accelerate the transfer of the new paradigm for device architecture from the laboratory to the R and D department.Increasing integration and logical complexity and shrinking the size and the power requirements of computational networks are key desiderata of current information technology. There is therefore a world-wide intense research effort aiming at computing at the nano-scale, using both classical and quantum computing approaches (5-17). These advances are made possible by a complementary effort on building atomic device...

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