Field effect

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

Controlling field-effect mobility in pentacene-based transistors by supersonic molecular-beam deposition

Abstract: We show that pentacene field-effect transistors, fabricated by supersonic molecular beams, have a performance strongly depending on the precursor’s kinetic energy (KE). The major role played by KE is in achieving highly ordered and flat films. In the range KE≈3.5–6.5eV, the organic field effect transistor linear mobility increases of a factor ∼5. The highest value (1.0cm2V−1s−1) corresponds to very uniform and flat films (layer-by-layer type growth). The temperature dependence of mobility for films grown at KE>6eV recalls that of single crystals (bandlike) and shows an opposite trend for films grown at KE⩽5.5eV.

Isomeric carbazolocarbazoles: synthesis, characterization and comparative study in Organic Field Effect Transistors

Abstract: We report here the synthesis and characterization of a new family of isomeric carbazolocarbazole derivatives, namely carbazolo[1,2-a]carbazole, carbazolo[3,2-b]carbazole and carbazolo[4,3-c]carbazole. Thermal, optical, electrochemical, morphological and semiconducting properties have been studied to understand the influence of geometrical isomerism on the optoelectronic properties of these compounds. Different packing patterns have been observed by single crystal X-ray diffraction (XRD) which then correlate with the different morphologies of the evaporated thin films studied by XRD and Atomic Force Microscopy (AFM). The effect of N-substituents has also been evaluated for one of the isomers revealing a noticeable influence on the performance as organic semiconductors in Organic Field Effect Transistors (OFETs). A good p-channel field effect has been determined for N,N′-dioctylcarbazolo[4,3-c]carbazole with a mobility of 0.02 cm2 V−1 s−1 and Ion/Ioff ratio of 106 in air. These preliminary results demonstrate the promising properties of molecular carbazolocarbazole systems which should be further explored in the area of organic semiconducting materials.

Negative differential conductivity and isothermal drain breakdown of the GaAs MESFET

Abstract: Electrical breakdown in GaAs MESFET's is simulated by two-dimensional (2-D) quasi hydrodynamic isothermal model with two types of carriers and "mixed" boundary conditions on the contacts-fixed drain current and fixed gate bias. It was demonstrated, that when some maximum drain voltage is reached the MESFET's differential conductivity becomes negative at every gate bias. The negative differential conductivity (NDC) is caused by the electric field reconstruction in the buffer by the injected carrier space charge. It is shown that the suggested breakdown model corresponds to the experimentally observed properties of the drain breakdown of the GaAs MESFET. The instantaneous burnout of the GaAs MESFET at the drain breakdown is explained by the uncontrollable drain current increase due to the NDC formation.

Nitride semiconductor device

Abstract: PROBLEM TO BE SOLVED: To greatly reduce piezo electric field effect, and to obtain a GaN-based semiconductor device with large light-emitting efficiency by performing inclined doping for reducing the concentration of impurities monotonously or in steps to the barrier layer of an MQW active layer. SOLUTION: A buffer layer 2 is deposited onto a substrate 1 for increasing temperature, thus sequentially laminating an AlGaN layer 3, an nAlGaN cladding layer 4, an nGaN light guide layer 5, a multiple quantum well(MQW) active layer 8, and a pGaN contact layer 9. In this case, the concentration of Si that is n-type impurities in the band structure of the MQW active layer 6 and a barrier layer is reduced from 5×1018 cm-3 or the like successively or in steps. Also, doping is made merely at the side of the substrate (an n- cladding side). In either case, it is important that the concentration of the Si at the n-cladding side is high. Doping is made in this manner, thus greatly and effectively canceling a piezo electric field being generated by strain.

Investigations on electroresistance effect in epitaxial manganite films using field effect configurations

Abstract: The influence of static electric field on the transport properties in La0.7A0.3MnO3 (A=Ca,Ba) epitaxial thin films was investigated by using field effect configurations (FEC). A single layer manganite film was deposited on LaAlO3 (LAO) substrate by pulsed laser deposition technique, and then a simple FEC was formed on it using the lithography technique, in which the manganite film was used as a channel, and the LAO substrate as a gate. Surprising results were achieved by employing such a FEC. The transport resistance increases with a positive gate voltage but decreases with a negative bias, which means the electroresistance (ER) effect changes sign with the field direction. The observed reduction of resistivity for the La0.7Ca0.3MnO3 and La0.7Ba0.3MnO3 channels reaches ∼32% and ∼34% upon a bias of −80 and −300V, respectively. The films could completely return to their pristine state after the bias was removed and the ER effect could be fully reproduced.