Monolayer-Bulk Black Phosphorus Natural Heterojunction Tunnel Field-Effect Transistor for Low Power Switches

Transistor down-scaling by Moore’s law over fifty years enabled today’s information technology, but fundamental limits have ended Moore’s law [1]; Transistors require at least 60 mV switching voltage for each 10-fold current increase (subthreshold swing (SS) 60 mV/dec). Alternative tunnel field-effect transistors (TFETs) are widely studied to achieve a sub-thermionic SS and high I₆₀ (current where SS becomes 60 mV/dec) [2]. Heterojunction (HJ) TFETs bear promise to deliver high I60, but experimental results do not meet theoretical expectations due to interface problems in the HJs constructed from different materials. Here, we report a natural HJ-TFET with spatially varying layer thickness in black phosphorus (BP) without interface problems. We achieved record-low average SS over 4–5 decades of current, SS_{ave_4dec} ≈ 22.9 mV/dec and SS_{ave_5dec} ≈ 26.0 mV/dec with record-high I60 (= 0.65–1 μA/μm), paving the way for the application in low power switches.

[1] Mack, C. A., Fifty Years of Moore's Law, IEEE Trans. Semicond. Manuf. 24, 202 (2011) .
[2]. Vandenberghe, W. G. et. al., Figure of merit for and identification of sub-60 mV/decade devices. Appl. Phys. Lett. 102, 013510 (2013).