Field effect

About: Field effect is a research topic. Over the lifetime, 4018 publications have been published within this topic receiving 92613 citations.

Doped Organic Semiconductors: Trap‐Filling, Impurity Saturation, and Reserve Regimes

Abstract: A typical human being carries billions of silicon-based field-effect transistors in his/her pockets. What makes these transistors work is Fermi level control, both by doping and field effect. Organic semiconductors are the core of a novel flexible electronics age, but the key effect of doping is still little understood. Here, precise handling is demonstrated for molar doping ratios as low as 10−5 in p- and n-doped organic thin-films by vacuum co-sublimation, allowing comprehensive studying of the Fermi level control over the whole electronic gap of an organic semiconductor. In particular, dopant saturation and reserve regimes are observed for the first time in organic semiconductors. These results will allow for completely new design rules of organic transistors with improved long term stability and precise parameter control.

First-principles theory of field-effect doping in transition-metal dichalcogenides: Structural properties, electronic structure, Hall coefficient, and electrical conductivity

Abstract: Electrochemical doping in 2D transition-metal dichalcogenides (TDMs) aimed at creating field effect transistor (FET) conditions can allow one to explore interesting transport phenomena in reduced dimensionality. In this timely work, the authors thoroughly investigate from first principles how field-effect doping affects the structural properties, electronic structure, and Hall coefficient of mono- and few-layers TDMs. They show that (i) the models, typically, used to estimate the doping charge in FET devices cannot be applied to 2D TMDs and, (ii) given the multivalley nature of both the conduction and valence bands, small differences in the band structure can manifest in transport behavior that is very different from that predicted based on a single parabolic band.

Carrier-Type Modulation and Mobility Improvement of Thin MoTe2.

Abstract: A systematic modulation of the carrier type in molybdenum ditelluride (MoTe2) field-effect transistors (FETs) is described, through rapid thermal annealing (RTA) under a controlled O2 environment (p-type modulation) and benzyl viologen (BV) doping (n-type modulation). Al2O3 capping is then introduced to improve the carrier mobilities and device stability. MoTe2 is found to be ultrasensitive to O2 at elevated temperatures (250 °C). Charge carriers of MoTe2 flakes annealed via RTA at various vacuum levels are tuned between predominantly pristine n-type ambipolar, symmetric ambipolar, unipolar p-type, and degenerate-like p-type. Changes in the MoTe2-transistor performance are confirmed to originate from the physical and chemical absorption and dissociation of O2, especially at tellurium vacancy sites. The electron branch is modulated by varying the BV dopant concentrations and annealing conditions. Unipolar n-type MoTe2 FETs with a high on–off ratio exceeding 106 are achieved under optimized doping conditions. By introducing Al2O3 capping, carrier field effect mobilities (41 for holes and 80 cm2 V−1 s−1 for electrons) and device stability are improved due to the reduced trap densities and isolation from ambient air. Lateral MoTe2 p–n diodes with an ideality factor of 1.2 are fabricated using the p- and n-type doping technique to test the superb potential of the doping method in functional electronic device applications.

Electronic and opto-electronic devices fabricated from nanostructured high surface to volume ratio thin films

Abstract: An electronic or opto-electronic device or a chemical sensor comprising: an interpenetrating network of a nanostructured high surface area to volume ratio film material and an organic/inorganic material forming a nanocomposite. The high surface area to volume film material is obtained onto an electrode substrate first, such that the nano-scale basic elements comprising this film material are embedded in a void matrix while having electrical connectivity with the electrode substrate. For example, the film material may comprise an array of nano-protrusions electrically connected to the electrode substrate and separated by a void matrix. The interpenetrating network is formed by introducing an appropriate organic/inorganic material into the void volume of the high surface area to volume film material. Further electrode(s) are defined onto the film or intra-void material to achieve a certain device. Charge separation, charge injection, charge storage, field effect devices, ohmic contacts, and chemical sensors are possible.

High performance ZnO nanowire field effect transistor using self-aligned nanogap gate electrodes

Abstract: A field effect transistor (FET) using a zinc oxide nanowire with significantly enhanced performance is demonstrated. The device consists of single nanowire and self-aligned gate electrodes with well defined nanosize gaps separating them from the suspended nanowire. The fabricated FET exhibits excellent performance with a transconductance of 3.06μS, a field effect mobility of 928cm2∕Vs, and an on/off current ratio of 106. The electrical characteristics are the best obtained to date for a ZnO transistor. The FET has a n-type channel and operates in enhancement mode. The results are close to those reported previously for p-type carbon nanotube (CNT) FETs. This raises the possibility of using ZnO as the n-type FET with a CNT as the p-type FET in nanoscale complementary logic circuits.