Embedded gate CVD MoS2 microwave FETs

Abstract

Recent studies have increased the cut off frequencies achievable by exfoliated MoS 2 by employing a combination of channel length scaling and geometry modification. However, for industrial scale applications, the mechanical cleavage process is not scalable but, thus far, the same device improvements have not been realized on chemical vapor deposited MoS 2 . Here we use a gate-first process flow with an embedded gate geometry to fabricate short channel chemical vapor deposited MoS 2 radio frequency transistors with a notable f T of 20 GHz and f max of 11.4 GHz, and the largest high-field saturation velocity, v sat = 1.88 × 10 6 cm/s, in MoS 2 reported so far. The gate-first approach, facilitated by cm-scale chemical vapor deposited MoS 2 , offers enhancement mode operation, I ON /I OFF ratio of 10 8 , and a transconductance (g m ) of 70 μS/μm. The intrinsic f T (f max ) obtained here is 3X (2X) greater than previously reported top-gated chemical vapor deposited MoS 2 radio frequency field-effect transistors. With as-measured S-parameters, we demonstrate the design of a GHz MoS 2 -based radio frequency amplifier. This amplifier has gain greater then 15 dB at 1.2 GHz, input return loss > 10 dB, bandwidth > 200 MHz, and DC power consumption of~10 mW.

Large-signal model of 2DFETs: compact modeling of terminal charges and intrinsic capacitances

“…Large area atomic single layer CVD MoS 2 , grown by a standard vapor transfer process as described in ref. , 27 was then transferred by poly(methyl methacrylate)-assisted wet transfer. Phosphoric acid etching was used to connect the embedded gate fingers and the gate pad.…”

Progress in Contact, Doping and Mobility Engineering of MoS2: An Atomically Thin 2D Semiconductor

“…MoS 2 can also be combined with conventional 3D semiconductors (such as Si and III-Vs), other 2D materials (e.g., TMDCs or graphene), and 1D and 0D materials to form various 2D/3D, 2D/2D, 2D/1D and 2D/0D vdW heterostructure devices, respectively, enabling a wide gamut of functionalities [52][53][54][55][56][57][58][59]. Indeed, several device applications such as ultra-scaled FETs [60][61][62][63], digital logic [64][65][66][67], memory [68][69][70][71], analog/RF [72][73][74][75], conventional diodes [76][77][78][79], photodetectors [80][81][82][83], light emitting diodes (LEDs) [84][85][86][87], lasers [88,89], photovoltaics [90][91][92][93], sensors [94][95][96][97], ultra-low-power tunneling-devices such as tunnel-FETs (TFETs)…”

Scalable high performance radio frequency electronics based on large domain bilayer MoS2

“…However, despite tremendous interest in graphene transistors for active radio frequency (RF) components 11 , 12 , it still remains a challenging issue that the gapless nature of graphene gives rise to poor current saturation and large output conductance in these transistors, which are detrimental for amplifying and mixing high frequency signals. Recently, great progress has been made on high frequency transistors and circuits based on 2D transition metal dichalcogenides, such as molybdenum disulfide (MoS 2 ), where the key disadvantage of graphene can be overcome 13 – 17 . Mechanically exfoliated MoS 2 on quartz substrates has shown high extrinsic radio frequency performances 13 .…”

“…In order to provide a low-cost scalable solution, large-area synthesis of MoS 2 atomic films by chemical vapor deposition (CVD) was developed with progressive improvement by many research groups 18 – 25 . Recently, RF transistors on flexible polyimide substrates based on monolayer MoS 2 grown by CVD exhibited an extrinsic cut-off frequency f T of 2.7 GHz and maximum oscillation frequency f max of 2.1 GHz 16 and, furthermore, an extrinsic f T of 3.3 GHz and f max of 9.8 GHz were demonstrated using an embedded gate structure on SiO 2 /Si substrates 17 . However, these parameters are still well below the devices based on exfoliated MoS 2 , severely limiting their high frequency applications.…”

“…A back-gated MoS 2 transistor with 40 nm channel length exhibits a record high ON-current ( I on ) of 1.52 mA μm −1 at 4.3 K with optimized high- κ dielectrics. State-of-the-art RF transistors based on bilayer MoS 2 are demonstrated with a record high extrinsic cut-off frequency f T of 7.2 GHz and maximum oscillation frequency f max of 23 GHz 15 – 17 . Moreover, MoS 2 RF transistors and frequency mixers on flexible substrates are demonstrated with a f T of 4 GHz and f max of 9 GHz where the mixer remains functional in gigahertz regime.…”