Reliability of next-generation field-effect transistors with transition metal dichalcogenides

Illarionov, Yu. Yu.; Molina‐Mendoza, Aday J.; Waltl, Michael; Knobloch, Theresia; Furchi, Marco M.; Mueller, Thomas

doi:10.1109/irps.2018.8353605

Cited by 5 publications

(4 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The use in space electronics, sensors, batteries, photovoltaics or light sources requires qualifications against vibrations and shocks, vacuum and thermal cycles, and exposure to radiation. In general, vibrations and shocks are not a threat for nanodevices and vacuum and thermal cycles are widely experimented in laboratories [9][10][11][12] . Similarly, the effect of radiation has been largely investigated for graphene [13][14][15][16] and well-known TMDs, such as 𝑀𝑜𝑆 2 , 𝑊𝑆 2 , 𝑀𝑜𝑆𝑒 2 , and 𝑊𝑆𝑒 2 13,[17][18][19][20][21][22] , although most of the irradiation studies have been carried out using high energy protons, ions, electrons or 𝛾 beams, typically in the 𝑀𝑒𝑉 range.…”

Section: Introductionmentioning

confidence: 99%

Electron irradiation of multilayer PdSe₂ field effect transistors

et al. 2020

View full text Add to dashboard Cite

Palladium diselenide (𝑃𝑑𝑆𝑒 2 ) is a recently isolated layered material that has attracted a lot of interest for the pentagonal structure, the air stability and the electrical properties largely tunable by the number of layers. In this work, 𝑃𝑑𝑆𝑒 2 is used in the form of multilayer as the channel of back-gate field-effect transistors, which are studied under repeated electron irradiations. Source-drain 𝑃𝑑 leads enable contacts with resistance below 350 𝑘Ω • 𝜇𝑚. The transistors exhibit a prevailing n-type conduction in high vacuum, which reversibly turns into ambipolar electric transport at atmospheric pressure. Irradiation by 10 𝑘𝑒𝑉 electrons suppresses the channel conductance and promptly transforms the device from n-type to p-type. An electron fluence as low as 160 𝑒 − /𝑛𝑚 2 dramatically change the transistor behavior demonstrating a high sensitivity of 𝑃𝑑𝑆𝑒 2 to electron irradiation. The sensitivity is lost after few exposures, that is a saturation condition is reached for fluence higher than ∼ 4000 𝑒 − /𝑛𝑚 2 . The damage induced by high electron fluence is irreversible as the device persist in the radiation-modified state for several hours, if kept in vacuum and at room temperature. With the support of numerical simulation, we explain such a behavior by electron-induced Se atom vacancy formation and charge trapping in slow trap states at the 𝑆𝑖/𝑆𝑖𝑂 2 interface.

show abstract

Section: Introductionmentioning

confidence: 99%

Electron irradiation of multilayer PdSe₂ field effect transistors

et al. 2020

View full text Add to dashboard Cite

show abstract

“…For the application of field-effect transistors (FETs), monolayer WS2 FETs are predicated to outperform other TMD FETs in terms of the on-state current density (JD,on) for both p-and n-type transistors (~2,800 μA/μm for the monolayer WS2 versus 2,200 -2,400 μA/μm for the monolayer MoS2, MoSe2, and MoTe2 FETs) 11 . In addition to the carrier mobility, the pristine hysteresis width of WS2 during reliability tests is the lowest compared to MoS2, MoSe2 and MoTe2 FETs 12 . The current on/off ratio at room temperature has been experimentally demonstrated up to ~10 6 for the monolayer WS2 FETs 13,14 and to ~10 8 for the multilayer WS2 FETs 15 .…”

Section: Introductionmentioning

confidence: 95%

Enhanced carrier transport by transition metal doping in WS₂ field effect transistors

et al. 2020

View full text Add to dashboard Cite

High contact resistance is one of the primary concerns for electronic device applications of two-dimensional (2D) layered semiconductors. Here, we explore the enhanced carrier transport through metal-semiconductor interfaces in WS2 field effect transistors (FETs) by introducing a typical transition metal, Cu, with two different doping strategies: (i) a "generalized" Cu doping by using randomly distributed Cu atoms along the channel and (ii) a "localized" Cu doping by adapting an ultrathin Cu layer at the metal-semiconductor interface. Compared to the pristine WS2 FETs, both the generalized Cu atomic dopant and localized Cu contact decoration can provide a Schottky-to-Ohmic contact transition owing to the reduced contact resistances by 1 -3 orders of magnitude, and consequently elevate electron mobilities by 5 -7 times higher. Our work demonstrates that the introduction of transition metal can be an efficient and reliable technique to enhance the carrier transport and device performance in 2D TMD FETs. IntroductionTungsten disulfide (WS2) with a semiconducting 2H phase is one of two-dimensional (2D) transition metal dichalcogenides (TMDs) exhibiting a series of unique properties, such as strong spin-orbit coupling, band splitting, and high nonlinear susceptibility 1-3 . Especially for future nanoelectronic applications, WS2 stands out as a promising channel material compared to other 2D semiconductors. For example, WS2 has a direct bandgap of 1.4 -2.0 eV 4-7 for the monolayer and an indirect bandgap of 1.2 -1.3 eV 4-6 for the bulk crystals. The carrier mobility of WS2 has been theoretically predicated up to ~5,300 cm 2 /Vs at 77 K 8 and ~700 -1,100 cm 2 /Vs at room temperature 8,9 , which exceeds most of the commonly used semiconducting TMDs such as MoS2 (340 cm 2 /Vs), MoSe2 (240 cm 2 /Vs), WSe2 (705 cm 2 /Vs), owing to the relatively small effective mass (0.34m0 for electrons and 0.46m0 for holes, where m0 is the free electron mass) 7 . Although the experimentally demonstrated electron mobilities, limited by Coulomb impurities, charge traps, surface defects and roughness, are much lower than the theoretical predication, new techniques have been developed to practically improve the mobility, for example, by exploiting h-BN 10 or high-k 11 dielectrics. For the application of field-effect transistors (FETs), monolayer WS2 FETs are predicated to outperform other TMD FETs in terms of the on-state current density (JD,on) for both p-and n-type transistors (~2,800 μA/μm for the monolayer WS2 versus 2,200 -2,400 μA/μm for the monolayer MoS2, MoSe2, and MoTe2 FETs) 11 . In addition to the carrier mobility, the pristine hysteresis width of WS2 during reliability tests is the lowest compared to MoS2, MoSe2and MoTe2 FETs 12 . The current on/off ratio at room temperature has been experimentally demonstrated up to ~10 6 for the monolayer WS2 FETs 13,14 and to ~10 8 for the multilayer WS2 FETs 15 . A nearly ideal subthreshold swing (SS) of 70 mV/decade at room temperature has been demonstrated in a simple back-gated WS2 FET th...

show abstract

“…This is attributed to versatile properties, such as astonishing electrostatic gate coupling and a high effective mass of electrons, leading to less direct tunneling leakage, no dangling bonds, and genuine optical/chemical properties [3][4][5][6]. With regard to the development of next-generation semiconductors, device instability is a mandatory issue to be resolved for practical applications at the circuit and system levels, and therefore, understanding the origins of device instability should be a priority [7][8]. Moreover, the reliability issue for next-generation semiconductors is a key challenge because newly explored materials are not mature enough; therefore, there is much room for improvement in material properties, process compatibility with Si technology, and wafer-scaled scalability, extending toward device-and circuit-level operation.…”

Section: Introductionmentioning

confidence: 99%

Unscrambling for Subgap Density-of-States in Multilayered MoS₂Field Effect Transistors under DC Bias Stress via Optical Charge-Pumping Capacitance-Voltage Spectroscopy

et al. 2021

View full text Add to dashboard Cite

Herein, we quantitatively analyze the evolution of the subgap density of states (DOSs) for multilayered molybdenum disulfide (m-MoS2) field effect transistors (FETs) with bilayered SiNx/SiOx gate dielectrics under positive bias stress (PBS) and negative bias stress (NBS) by using optical charge-pumping capacitance-voltage spectroscopy. To decouple external gas ambient effects on device instability, hydrophobic fluoropolymers (cyclized transparent optical polymer; CYTOP) are employed for m-MoS2 FETs followed by the evaluation of subgap-DOSs in the devices for the respective PBS (or NBS). Through extraction of subgap-DOSs and their deconvolution with an analytical model of acceptor (or donor)-like states, it is shown that the device instability is closely correlated with state transitions of DOSs, corresponding to shallow (or midgap) levels for monosulfur vacancy (VS) (or disulfur vacancy (VS2)). Moreover, after PBS, the initial states of VS (0) (or HS2 (0)) transit toward VS (−1) (or HS2 (−1)) via electron trapping, whereas the transition toward VS (0) and HS2 (+1) during NBS is assessed from the initial VS (−1) and HS2 (0) states. Furthermore, technology computer-aided design (TCAD) simulation based on the extracted DOSs properly replicates the measured I-V characteristics of m-MoS2 FETs with (and without) CYTOP encapsulation. In this study, subgap-DOS characterization via optical charge pumping and validation of the quantitative evolution of subgap-DOSs suggest that this platform can be potentially beneficial for an in-depth understanding of the origins of device instability for transition metal dichalcogenide (MX2)-based FETs, where M is a transition metal and X is a chalcogenide.INDEX TERMS MoS2, field effect transistor, density of state (DOS), bias stress instability, TCAD simulation

show abstract

Reliability of next-generation field-effect transistors with transition metal dichalcogenides

Cited by 5 publications

References 29 publications

Electron irradiation of multilayer PdSe₂ field effect transistors

Electron irradiation of multilayer PdSe₂ field effect transistors

Enhanced carrier transport by transition metal doping in WS₂ field effect transistors

Unscrambling for Subgap Density-of-States in Multilayered MoS₂Field Effect Transistors under DC Bias Stress via Optical Charge-Pumping Capacitance-Voltage Spectroscopy

Contact Info

Product

Resources

About

Reliability of next-generation field-effect transistors with transition metal dichalcogenides

Cited by 5 publications

References 29 publications

Electron irradiation of multilayer PdSe2 field effect transistors

Electron irradiation of multilayer PdSe2 field effect transistors

Enhanced carrier transport by transition metal doping in WS2 field effect transistors

Unscrambling for Subgap Density-of-States in Multilayered MoS2Field Effect Transistors under DC Bias Stress via Optical Charge-Pumping Capacitance-Voltage Spectroscopy

Contact Info

Product

Resources

About

Electron irradiation of multilayer PdSe₂ field effect transistors

Electron irradiation of multilayer PdSe₂ field effect transistors

Enhanced carrier transport by transition metal doping in WS₂ field effect transistors

Unscrambling for Subgap Density-of-States in Multilayered MoS₂Field Effect Transistors under DC Bias Stress via Optical Charge-Pumping Capacitance-Voltage Spectroscopy