Abstract
Field effect transistors (FETs) using two-dimensional molybdenum disulfide (MoS2) as the channel material has been considered one of the most potential candidates for future complementary metal-oxide-semiconductor technology with low power consumption. However, the understanding of the correlation between the device performance and material properties, particularly for devices with scaling-down channel lengths, is still insufficient. We report in this paper back-gate FETs with chemical-vapor-deposition grown and transferred MoS2 and Zr doped HfO2 ((Hf,Zr)O2, HZO) high-k dielectric gates with channel lengths ranging from 10 to 30 µm with a step of 5 µm. It has been demonstrated that channels with the length to width ratio of 0.2 lead to the most superior performance of the FETs. The MoS2/HZO hybrid FETs show a stable threshold voltage of ∼1.5 V, current on/off ratio of >104, and field effect mobility in excess of 0.38 cm2 V−1 s−1. The impact of the channel lengths on FET performance is analyzed and discussed in depth. A hysteresis loop has been observed in the Ids − Vgs characteristics of the hybrid FETs, which has been further studied and attributed to the charge effect at the interfaces. The HZO films show a relatively weak ferroelectric orthorhombic phase and thus serve mainly as the high-k dielectric gate. Charge trapping in the HZO layer that might induce hysteresis has been discussed. Our results show that MoS2/HZO hybrid FETs possess great potential in future low power and high-speed integrated circuits, and future work will focus on further improvement of the transistor performances using ferroelectric HZO films and the study of devices with even shorter MoS2 channels.
Highlights
The continuous scaling-down of the integrated circuits (ICs) and transistors leads to increasing power consumption
The difference between E2g1 and A1g is 19.5 cm−1, which is in good agreement with the reported mode difference of the MoS2.21,22 The scanning electron microscope (SEM) image of the MoS2/HZO surface, as shown in Fig. 1(b), demonstrated that the MoS2 surface was uniform and a few defects were observed in a large scale
The electrical properties of devices with channel lengths ranging from 10 to 30 μm with a step of 5 μm have been studied in detail
Summary
The continuous scaling-down of the integrated circuits (ICs) and transistors leads to increasing power consumption. According to the International Technology Roadmap for Semiconductors (ITRS), Molybdenum disulphide (MoS2), together with graphene and boron nitride, is a potential new material for integration into nanometer scale structures due to its ultra-thin structure and outstanding electrical properties.. MoS2 and WSe2 have relatively higher carrier scitation.org/journal/adv mobility (up to ∼200 cm V−1 s−1), while MoS2 is currently the most studied one due to its outstanding electrical and optoelectronic properties.. MoS2 could be fabricated by chemical vapor deposition (CVD), which is capable of forming large scale monolayers to multilayers with uniform morphology and remarkable optical, electrical, and optoelectronic properties. CVD MoS2 with higher mobility is more favorable in electronic devices.
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