Jonathan Klamkin - US grants

Microprocessors containing billions of transistor switches are at the heart of PCs, cell phones, computer servers answering our internet searches, and supercomputers modeling the weather and designing new drugs and aircraft. Modern machinery is controlled by microprocessors; a typical car uses 50. After 50 years of rapid improvement, since 2000 progress has stalled, primarily because the transistors consume too much energy when they switch. As transistors are made smaller, more fit on a chip, and the energy consumed increases. The battery is drained quickly and chip becomes hot. Slowing the switching reduces heating, but then the software runs slowly. In this program, a new transistor design will be investigated. If successful, these transistors will consume 100 times less switching energy, allowing faster, more powerful chips.

The challenge is the power supply voltage; reducing the voltage by 2:1 reduces the switching energy 4:1. Between ~1990-2005, voltages were reduced from 5 to 1 Volt. Unfortunately, with normal (MOS) transistor switches, below ~0.7 Volts the transistor's switching becomes imperfect, with the transistor not turning completely off. This finite off-state leakage current increases energy consumption, hence it has not been possible to supplies much below 0.7 Volts. Ten years ago, tunnel transistors were proposed, as these can turn off nearly completely even at supplies as low as 0.3 Volts. Unfortunately, tunnel transistors do not turn on well, and microprocessors using them will therefore operate slowly. This limitation becomes much worse if the supply is dropped to 0.1 Volts. This program will research a new design, the triple-heterojunction tunnel transistor. This has added semiconductor junction layers which increased the on-current by as much as 100:1. If successful, rapidly-switching microprocessors will be feasible with even a 0.07V supply, and would consume as little as 1% of the energy of today's technology.