High-mobility suspended MoS₂ devices with tunable threshold voltage

Abstract

Molybdenum disulfide (MoS₂) is regarded as a promising next-generation semiconductor material for high-end microelectronic chips due to its excellent properties. However, due to the atomic thickness of two-dimensional materials (2DMs), the interactions between these materials and their supporting substrates cannot be ignored, which affects the intrinsic properties of 2DMs. In this work, we investigated the influence of the substrate on the performance of MoS₂ devices. As compared to supported MoS₂ field-effect transistors (FETs), the suspended MoS₂ FET exhibits more intrinsic properties of a threshold voltage (V_th) shift toward 0 V and the current on/off ratio increases by 3 orders of magnitude. Moreover, by varying the trench/channel ratio in the MoS₂ FETs, we can effectively modulate the electrical performance of MoS₂. An increase in the trench/channel ratio results in a shift of the V_th from −40 to −5 V, approaching the ideal value. Concurrently, the subthreshold swing is reduced by approximately an order of magnitude to ~200 mV dec^–1 (from ~3600 mV/dec), and the mobility is enhanced from ~1 to 100 cm² V⁻¹ s⁻¹. To mitigate the effects of contact resistance and other extrinsic factors, we fabricated a suspended Hall-bar MoS₂ device, achieving a mobility of 96.8 cm² V⁻¹ s⁻¹, more than double the 37.0 cm² V⁻¹ s⁻¹ measured in a supported device. This work demonstrates a practical approach for enhancing the properties of 2D semiconductor devices, facilitating the development of high-performance electronics.

Keywords

field-effect transistors / MoS₂ / suspended / threshold voltage / two-dimensional materials

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