Researchers from South Korea, Japan, and the United Kingdom have fabricated a half-adder logic circuit using only five transistors. "We made the first successful implementation of a one-electron-based half-adder (HA) that is the smallest arithmetic block for the single-electron transistor (SET) multi-valued logic family," says Chungbuk National University professor Jung-Bum Choi.
The HA, the smallest type of logic circuit, operates at nA-levels with low-power consumption, and is multi-valued and flexible. "Therefore, the one-electron HA cell will provide a basis for ultra-high density and low-power ultra-large-scale integration, which is one of the most critical problems facing future small mobile IT systems," Choi says.
The team used three SETs and two field-effect transistors (FET), compared with 20 FETs in a traditional CMOS HA. The scientists demonstrated that the HA mode could be switched to a subtraction mode simply by changing the control gate on an SET. In subtraction mode, the sum and carry functions became difference and borrow functions.
The HA logic cell also offers fast operation, and Choi believes it could be useful for next-generation terabit-level nanoelectronics. The researchers are now working to operate the logic circuit at room temperature.
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