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Novel field-effect Schottky barrier transistors based on graphene-MoS2 heterojunctions.

Tian H, Tan Z, Wu C, Wang X, Mohammad MA, Xie D, Yang Y, Wang J, Li LJ, Xu J, Ren TL - Sci Rep (2014)

Bottom Line: Recently, two-dimensional materials such as molybdenum disulphide (MoS2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio.Moreover, the field effective mobility of the FESBT is up to 58.7 cm(2)/V · s.Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature.

View Article: PubMed Central - PubMed

Affiliation: 1] Institute of Microelectronics, Tsinghua University, Beijing 100084, China [2] Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China [3].

ABSTRACT
Recently, two-dimensional materials such as molybdenum disulphide (MoS2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio. However, the carrier mobility in backgate MoS2 FET is rather low (typically 0.5-20 cm(2)/V · s). Here, we report a novel field-effect Schottky barrier transistors (FESBT) based on graphene-MoS2 heterojunction (GMH), where the characteristics of high mobility from graphene and high on-off ratio from MoS2 are properly balanced in the novel transistors. Large modulation on the device current (on/off ratio of 10(5)) is achieved by adjusting the backgate (through 300 nm SiO2) voltage to modulate the graphene-MoS2 Schottky barrier. Moreover, the field effective mobility of the FESBT is up to 58.7 cm(2)/V · s. Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature. This provides an opportunity to overcome the limitation of 60 mV/decade for conventional CMOS devices. The FESBT implemented with a high on-off ratio, a relatively high mobility and a low subthreshold promises low-voltage and low-power applications for future electronics.

No MeSH data available.


Related in: MedlinePlus

Comparison of our FESBT with state-of-the-art graphene transistors and back-gated MoS2 transistors.The graphene transistors have a high mobility but quite a low on/off ratio. The MoS2 transistors have a high on/off ratio but quite a low mobility. The FESBT combines the qualities of high mobility from graphene and high on-off ratio from MoS2.
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f6: Comparison of our FESBT with state-of-the-art graphene transistors and back-gated MoS2 transistors.The graphene transistors have a high mobility but quite a low on/off ratio. The MoS2 transistors have a high on/off ratio but quite a low mobility. The FESBT combines the qualities of high mobility from graphene and high on-off ratio from MoS2.

Mentions: In order to show the advance of our FESBT, the mobility and on/off ratio of the back-gated MoS2 transistors1631323334, graphene transistors353637 and FESBT are compared in Figure 6. The references are selected based on their reliability and similarity to the structure of our device. Especially, we use back-gated MoS2 transistors for comparison. Kaasbjerg et al.'s work found that the mobility of MoS2 at room temperature is limited down to ~410 cm2/V·s due to optical phonon scattering38. Additionally, some previous works investigated high-κ dielectric as top gate oxide, which has improved the mobility significantly39. The reason for the improvement of the MoS2 mobility was due to the introduction of “imaginary charges” to suppress the scattering potential40 and high-κ dielectric which enhanced the screening of impurity charges39. In order to compare with works in which a similar device structure is employed, we select the references in Figure 6 that only adopts SiO2 as a back gate dielectric. Our FESBT has a mobility up to 58.7 cm2/V·s with an on/off ratio of 105. Although the mobility of the graphene could be up to 105 cm2/V·s, the drawback of graphene transistors is the low on/off ratio (typically lower than 10). Most recently, MoS2 is developed to realize ultra-high on/off ratio up to 108. But the state-of-the-art mobility of MoS2 is still lower than 20 cm2/V·s. FESBT devices occupy a trade-off space between high mobility and considerable on-off ratio, which are separately realized by graphene transistors and MoS2 transistors in previous works. Also as a two-dimensional device, FESBT has potential in high-performance flexible electronics. Combining these advantages together with its predictable low subthreshold swing, FESBT devices should have opportunities in next-generation electronics for low-voltage, low-power and flexible applications.


Novel field-effect Schottky barrier transistors based on graphene-MoS2 heterojunctions.

Tian H, Tan Z, Wu C, Wang X, Mohammad MA, Xie D, Yang Y, Wang J, Li LJ, Xu J, Ren TL - Sci Rep (2014)

Comparison of our FESBT with state-of-the-art graphene transistors and back-gated MoS2 transistors.The graphene transistors have a high mobility but quite a low on/off ratio. The MoS2 transistors have a high on/off ratio but quite a low mobility. The FESBT combines the qualities of high mobility from graphene and high on-off ratio from MoS2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4127518&req=5

f6: Comparison of our FESBT with state-of-the-art graphene transistors and back-gated MoS2 transistors.The graphene transistors have a high mobility but quite a low on/off ratio. The MoS2 transistors have a high on/off ratio but quite a low mobility. The FESBT combines the qualities of high mobility from graphene and high on-off ratio from MoS2.
Mentions: In order to show the advance of our FESBT, the mobility and on/off ratio of the back-gated MoS2 transistors1631323334, graphene transistors353637 and FESBT are compared in Figure 6. The references are selected based on their reliability and similarity to the structure of our device. Especially, we use back-gated MoS2 transistors for comparison. Kaasbjerg et al.'s work found that the mobility of MoS2 at room temperature is limited down to ~410 cm2/V·s due to optical phonon scattering38. Additionally, some previous works investigated high-κ dielectric as top gate oxide, which has improved the mobility significantly39. The reason for the improvement of the MoS2 mobility was due to the introduction of “imaginary charges” to suppress the scattering potential40 and high-κ dielectric which enhanced the screening of impurity charges39. In order to compare with works in which a similar device structure is employed, we select the references in Figure 6 that only adopts SiO2 as a back gate dielectric. Our FESBT has a mobility up to 58.7 cm2/V·s with an on/off ratio of 105. Although the mobility of the graphene could be up to 105 cm2/V·s, the drawback of graphene transistors is the low on/off ratio (typically lower than 10). Most recently, MoS2 is developed to realize ultra-high on/off ratio up to 108. But the state-of-the-art mobility of MoS2 is still lower than 20 cm2/V·s. FESBT devices occupy a trade-off space between high mobility and considerable on-off ratio, which are separately realized by graphene transistors and MoS2 transistors in previous works. Also as a two-dimensional device, FESBT has potential in high-performance flexible electronics. Combining these advantages together with its predictable low subthreshold swing, FESBT devices should have opportunities in next-generation electronics for low-voltage, low-power and flexible applications.

Bottom Line: Recently, two-dimensional materials such as molybdenum disulphide (MoS2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio.Moreover, the field effective mobility of the FESBT is up to 58.7 cm(2)/V · s.Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature.

View Article: PubMed Central - PubMed

Affiliation: 1] Institute of Microelectronics, Tsinghua University, Beijing 100084, China [2] Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China [3].

ABSTRACT
Recently, two-dimensional materials such as molybdenum disulphide (MoS2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio. However, the carrier mobility in backgate MoS2 FET is rather low (typically 0.5-20 cm(2)/V · s). Here, we report a novel field-effect Schottky barrier transistors (FESBT) based on graphene-MoS2 heterojunction (GMH), where the characteristics of high mobility from graphene and high on-off ratio from MoS2 are properly balanced in the novel transistors. Large modulation on the device current (on/off ratio of 10(5)) is achieved by adjusting the backgate (through 300 nm SiO2) voltage to modulate the graphene-MoS2 Schottky barrier. Moreover, the field effective mobility of the FESBT is up to 58.7 cm(2)/V · s. Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature. This provides an opportunity to overcome the limitation of 60 mV/decade for conventional CMOS devices. The FESBT implemented with a high on-off ratio, a relatively high mobility and a low subthreshold promises low-voltage and low-power applications for future electronics.

No MeSH data available.


Related in: MedlinePlus