Chemical vapor deposited monolayer MoS₂top-gate MOSFET with atomic-layer-deposited ZrO₂as gate dielectric

Abstract

For the first time, ZrO2 dielectric deposition on pristine monolayer MoS2 by atomic layer deposition (ALD) is demonstrated and ZrO2/MoS2 top-gate MOSFETs have been fabricated. ALD ZrO2 overcoat, like other high-k oxides such as HfO2 and Al2O3, was shown to enhance the MoS2 channel mobility. As a result, an on/off current ratio of over 10(7), a subthreshold slope of 276 mV dec(-1), and a field-effect electron mobility of 12.1 cm(2) V-1 s(-1) have been achieved. The maximum drain current of the MOSFET with a top-gate length of 4 mu m and a source/drain spacing of 9 mu m is measured to be 1.4 mu A mu m(-1) at V-DS = 5 V. The gate leakage current is below 10(-2) A cm(-2) under a gate bias of 10 V. A high dielectric breakdown field of 4.9 MV cm(-1) is obtained. Gate hysteresis and frequency-dependent capacitance-voltage measurements were also performed to characterize the ZrO2/MoS2 interface quality, which yielded an interface state density of similar to 3 x 10(12) cm(-2) eV(-1).