Top-gate organic depletion and inversion transistors with doped channel and injection contact

Abstract

Organic field-effect transistors constitute a vibrant research field and open application perspectives in flexible electronics. For a commercial breakthrough, however, significant performance improvements are still needed, e.g., stable and high charge carrier mobility and on-off ratio, tunable threshold voltage, as well as integrability criteria such as n- and p-channel operation and top-gate architecture. Here, we show pentacene-based top-gate organic transistors operated in depletion and inversion regimes, realized by doping source and drain contacts as well as a thin layer of the transistor channel. By varying the doping concentration and the thickness of the doped channel, we control the position of the threshold voltage without degrading on-off ratio or mobility. Capacitance-voltage measurements show that an inversion channel can indeed be formed, e.g., an n-doped channel can be inverted to a p-type inversion channel with highly p-doped contacts. The Cytop polymer dielectric minimizes hysteresis, and the transistors can be biased for prolonged cycles without a shift of threshold voltage, indicating excellent operation stability.

Passivation of Molecular n‐Doping: Exploring the Limits of Air Stability

“…In particular, simultaneous processing of both p-and n-type doped transistors for organic complementary semiconductor technology [1][2][3] is critical since several process steps like photolithography are usually performed under ambient conditions rather than in inert atmosphere or vacuum. Exposing these devices to air might lead to oxidation or reduction of the π-conjugated organic molecules due to electron donation or acceptance to/from oxygen and/or water species, respectively.…”

Metal Halide Perovskites: Synthesis, Ion Migration, and Application in Field‐Effect Transistors

“…For instance, Yusoff et al used polymethyl methacrylate (PMMA) as the dielectric, because PMMA can be processed at a relatively low temperature and soluble in a perovskite‐orthogonal solvent . Also, Cytop as an amporhous fluoropolymer, which has been widely used in OFETs, can be also used in MHP‐FETs because of its perovskite‐orthogonal solvent and its negligible electron‐trapping OH groups …”

“…For instance, Yusoff et al used polymethyl methacrylate (PMMA) as the dielectric, because PMMA can be processed at a relatively low temperature and soluble in a perovskite-orthogonal solvent. [20] Also, Cytop as an amporhous fluoropolymer, which has been widely used in OFETs, [145,146] can be also used in MHP-FETs because of its perovskiteorthogonal solvent and its negligible electron-trapping OH groups. [22,147,148] Moreover, an external light source can be used as the fourth terminal electrode to further modulate the channel current controlled by the gate electrode, in order to obtain room-temperature MAPbI 3 -based transistors.…”

Controlling threshold voltage and leakage currents in vertical organic field-effect transistors by inversion mode operation

“…In this letter, we report on a vertical OFET (VOFET) 10,11 operating in inversion mode. [12][13][14][15] Variation of the doping concentration or thickness of the inversion layer allows to control the threshold voltage and Off state current of the VOFET without altering the geometry or material system as a whole.…”

“…For an n-type VOFET, it is therefore expected that a p-doped layer, placed into the accumulation region, will lead to an inversion operation in the same way as demonstrated previously for conventional p-type OFETs. 13,14 To check for the formation of this inversion regime, capacitance-voltage (CV) measurements are performed on a series of metal-insulator-semiconductor (MIS) capacitors, resembling a material stack identical to the channel region underneath the source electrode of the VOFET (see Fig. 1 for the VOFET geometry).…”