Through a process known as impact ionization, extra electric charges are generated inside transistors (as represented by the red electron and blue “hole” pair in this schematic n-channel metal oxide semiconductor field effect transistor or MOSFET). These pairs break up, and, at low temperatures, some of the positively charged holes are trapped in the transistor body, providing a way to store memory states. This impact ionization process underlies a novel proposed cryogenic memory.
Credit: NIST
Digital transistors – assembled by the billions in today’s computer chips – act as near-perfect electronic switches. In the “on” position, achieved when an above-threshold voltage is applied to the device, the transistor allows current to flow. When the switch is off, the transistor prevents the flow of current. The on/off positions of the switch translate into the 1s and 0s of digital computation.
Although these 1s and 0s are fundamental to the operation of a computer, complex computations require that the data be stored in memory in order to be useful. In today’s chips, memory relies on another device, in addition to the transistor: a capacitor that stores electric charge. The capacitor is empty when the transistor is switched off and flooded with electric charge when the transistor switches on. The charge on the capacitor then preserves the 1 or 0 of the transistor’s switch state.
Researchers at the National Institute of Standards and Technology (NIST) and their colleagues at Brown University have now observed that at temperatures about three degrees above absolute zero (3K), a transistor can serve as its own memory storage device, obviating the need for a capacitor. By a process known as impact ionization, extra electric charges are generated inside the transistor. At low temperatures, some of these extra charges can be trapped in the ..
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