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A Polycrystalline Silicon Thin-Film Transistor with Grain-Induced Stochasticity for an Energy-Efficient True Random
Seung-Il Kim1, In-Ki Hong1, Sang-Won Lee1
1School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon34141, Republic of Korea.
ACS Nano
|August 11, 2026
Summary
We demonstrate abnormal stochastic oscillation in polycrystalline silicon thin-film transistors (poly-Si TFTs) for the first time. This breakthrough enables compact, energy-efficient true random-number generators (tRNGs) with enhanced entropy from grain boundaries.
Area of Science:
- Materials Science
- Semiconductor Physics
- Microelectronics
Background:
- Metal oxide semiconductor field-effect transistors (MOSFETs) are traditionally used as switches and amplifiers.
- The potential of MOSFETs as oscillators, particularly polycrystalline silicon thin-film transistors (poly-Si TFTs), remains underexplored.
- Grain boundaries in poly-Si TFTs present challenges due to carrier recombination, hindering single transistor latch (STL) operation.
Purpose of the Study:
- To investigate and demonstrate stochastic oscillation in poly-Si TFTs.
- To utilize the unique properties of poly-Si TFTs for creating a novel entropy source.
- To develop a compact and energy-efficient true random-number generator (tRNG) based on these oscillations.
Main Methods:
- Optimized poly-Si deposition and annealing to increase grain size.
- Adjusted body doping concentration to enhance hole accumulation.
- Implemented and characterized single transistor latch (STL) phenomena and oscillations in poly-Si TFTs.
Main Results:
- Successfully achieved STL and STL-driven oscillations in monolithic 3D stackable poly-Si TFTs.
- Demonstrated that grain-boundary traps in poly-Si TFTs amplify oscillation randomness through stochastic carrier trapping/detrapping.
- Developed a poly-Si TFT-based tRNG that passed all NIST SP 800-22 randomness tests with high energy efficiency (0.21 pJ/bit).
Conclusions:
- Poly-Si TFTs can exhibit abnormal stochastic oscillations, overcoming previous limitations.
- Grain-boundary enhanced entropy in poly-Si TFTs provides a viable source for high-performance tRNGs.
- The developed tRNG is compact, energy-efficient, robust, and suitable for 3D monolithic integration with CMOS circuitry.
