Two-dimensional transistors with reconfigurable polarities for secure circuits

Security is a critical aspect in modern circuit design, but research into hardware security at the device level is rare as it requires modification of existing technology nodes. With the increasing challenges facing the semiconductor industry, interest in out-of-the-box security solutions has grown, even if this implies introducing novel materials such as two-dimensional layered semiconductors. Here, we show that high-performance, low-voltage, two-dimensional black phosphorus field-effect transistors (FETs) that have reconfigurable polarities are suitable for hardware security applications. The transistors can be dynamically switched between p-FET and n-FET operation through electrostatic gating and can achieve on–off ratios of 105 and subthreshold swings of 72 mV dec−1 at room temperature. Using the transistors, we create inverters that exhibit gains of 33.3 and are fully functional at a supply voltage of 0.2 V. We also create a security primitive circuit with polymorphic NAND/NOR obfuscation functionality with sub-1-V operation voltages, and the robustness of the polymorphic gate against power supply variations is tested using Monte Carlo simulations. Transistors that use two-dimensional black phosphorus as the active material can dynamically switch between p-type and n-type operation, and can be used to create security primitive circuits with polymorphic NAND/NOR obfuscation functionality.