High-Performance CVD Bilayer MoS2 Radio Frequency Transistors and Gigahertz Mixers for Flexible Nanoelectronics

Abstract

Two-dimensional (2D) MoS2 have attracted tremendous attention due to their potential applications in future flexible high-frequency electronics. Bilayer MoS2 exhibits the advantages of carrier mobility when compared with monolayer mobility, thus making the former more suitable for use in future flexible high-frequency electronics. However, there are fewer systematical studies of chemical vapor deposition (CVD) bilayer MoS2 radiofrequency (RF) transistors on flexible polyimide substrates. In this work, CVD bilayer MoS2 RF transistors on flexible substrates with different gate lengths and gigahertz flexible frequency mixers were constructed and systematically studied. The extrinsic cutoff frequency (fT) and maximum oscillation frequency (fmax) increased with reducing gate lengths. From transistors with a gate length of 0.3 μm, we demonstrated an extrinsic fT of 4 GHz and fmax of 10 GHz. Furthermore, statistical analysis of 14 flexible MoS2 RF transistors is presented in this work. The study of a flexible mixer demonstrates the dependence of conversion gain versus gate voltage, LO power and input signal frequency. These results present the potential of CVD bilayer MoS2 for future flexible high-frequency electronics.

Effect of Back-Gate Voltage on the High-Frequency Performance of Dual-Gate MoS2 Transistors

“…The achieved f T of 4.6 GHz and f max of 11.9 GHz were also further verified using Gummel’s method [ 45 ] and maximum available power gain (MAG) [ 46 ], as shown in Figure 5 b,d. The obtained cut-off frequency and maximum oscillation frequency were consistent with our previous reported work [ 16 ], demonstrating the potential of CVD bilayer MoS 2 for large-scale high-frequency circuit applications [ 27 , 35 ].…”

“…Although the implementation of the standard calibration method can move the measurement reference plane from the internal receiver of the vector network analyzer to the tip of the ground–signal–ground (GSG) probe, the parasitic capacitance, inductance, and resistance of the test electrodes also have a significant effect on the obtained S-parameters [ 27 , 47 ]. To eliminate the influence of the test electrodes on the measured S-parameters and to obtain the intrinsic RF performance of the MoS 2 RF transistor, this work uses the standard “open” and “short” structures for de-embedding [ 25 ].…”

“…Chemical-vapor-deposited bilayer MoS 2 was used as the channel material in the dual-gate MoS 2 RF transistors as it has higher carrier mobility, lower contact resistance and improved low-frequency noise when compared with CVD monolayer MoS 2 [ 16 , 27 , 35 ]. Additionally, the CVD method is one of the most promising methods for synthesizing large areas and high-quality MoS 2 .…”

“…The CVD bilayer MoS 2 films were grown on soda-lime-silica glass substrates with 1.4 g sulfur and 1.5 mg MoO 3 as the precursors at atmospheric pressure. The details about the CVD bilayer growth process, material imaging and crystal structure characterization have been reported in our previous works [ 16 , 27 ]. After the CVD growth process, bilayer MoS 2 films were transferred onto highly resistive Si substrates with atomic-layer-deposited (ALD) 20-nm HfLaO.…”

“…In 2018, based on high-quality CVD bilayer MoS 2 , high-frequency MoS 2 transistors with extrinsic maximum oscillation frequency of 23 GHz were demonstrated [ 16 ]. Gigahertz frequency mixer and amplifier based on MoS 2 high-frequency transistors were also constructed for potential RF circuit applications [ 16 , 27 ]. Those works demonstrated the potential of 2D MoS 2 for future novel high-frequency electronics.…”