Texas Instruments Inc gave the International Electron Devices meeting in San Francisco last week a resounding send-off by announcing that it had successfully fabricated Quantum Tunnelling Transistors in Gallium Arsenide. The circuits harness the otherwise troublesome phenomenon that when devices are laid out to very fine design rules, some electrons tunnel through the barriers between the current-carrying features on the chip. The Texas engineers have found a way of controlling this leakage of electrons but the circuits use design rules of 10 to 20 thousandths of a micron – 10 to 20 nanons? That means that a million transistors would occupy only a square centimetre of Gallium Arsenide. They are claimed to switch more than 1,000 times faster than conventional circuits, implying speeds of around a tenth of a picosecond. The Texas engineers are optimistic that they will have advanced the technology sufficiently that they will be able to fabricate hybrid chips that include the quantum tunnelling transistors for speed critical functions within the next five years or so.
