Low-power complementary inverter with negative capacitance 2D semiconductor transistors

Abstract

A fundamental limit for the supply voltage of conventional field-effect transistors is the long high-energy tail of the Boltzmann distribution of the carrier population at the source junction, which requires a gate voltage at least 60 mV to change one decade of current. Here 2D semiconductors are adopted as channel materials and hafnium zirconium oxide (HZO) as negative capacitance (NC) gate stack to realize low-power complementary logic inverter. With HZO/Al2O3 NC gate stack, the 2D semiconductor field-effect transistor (FET) shows an average subthreshold slope less than Boltzmann limit (as low as 18 mV dec−1) at room temperature for both forward and reverse gate voltage sweeps, which allows to reach the same ON-state current at a lower Vdd without increasing the OFF-state current. The drain current can be modulated by 5 × 104 within 220 mV, still exhibiting average SS below 60 mV dec−1. By constructing van der Waals contact to improve the charge injection and control the carrier type, unipolar p-type WSe2 FET with reduced hole Schottky barrier height is achieved. The complementary inverter with MoS2 and WSe2 NCFETs shows the power consumption of 68 pW.