Field Effect Transistor. JFET construction, Symbol, Basic operation, V-I Characteristics, Transfer Characteristics (Shockley's Equation), Cut-off & Pinch-off voltages, Transconductance, Input resistance & Capacitance. Drain to Source resistance. Biasing of JFET - Biasing against device variation, biasing for zero current drift. JFET data sheet specifications. JFET as an amplifier, small signal JFET model, analysis of CS, CD, CG amplifiers using small signal JFET model.
The active matrix OLED displays require thin-film transistors. In order to realize practical use of flexible displays, organic field-effect transistors (OFETs) are getting attentions since they can be fabricated on plastic at low temperature. We research for light emitting organic field-effect transistors, ambipolar organic field-effect transistors, and design new materials and device structures. Flexible Driving Circuit
Organic semiconductors offer the benefit that they can be printed on plastic, flexible substrates at low temperature by solution-based techniques, which would result in a practical use of flexible displays. Though the first OFETs did not transport charge carrier as efficient as inorganic semiconductors, now they are achieving charge carrier mobility of the same order as amorphous silicon.
Basic Structure of OFET
FET has a switching device configuration consisting of source-drain electrode, gate electrode, active layer and gate insulator. In the case of OFET, organic semiconductors are used as an active layer. Applying a gate voltage results either accumulation or inversion of charge carriers at the organic semiconductor / gate insulator interface. The current flowing between the source and drain electrodes is modulated by the gate voltage, which is also used to turn the device from the off to the on state. There have been developed a wide variety of p-type (hole transport) and n-type (electron transport) OFETs. We try to synthesize novel materials and design new devise architectures suitable for high performance OFETs.
Ambipolar OFETs can be operated either p- or n-type in a single organic semiconducting layer. These ambipolar properties are useful for fabricating logic circuit or light emitting devices. We have strong interest on charge carrier accumulation, transport mechanism under ambipolar operation.
In the LE-OFETs, holes and electrons recombine to generate molecular excitons and light in the middle of OFET channel. LE-OFETs contribute not only to increased apertures in the pixels of light-emitting elements but also the inexpensive fabrication of active matrix displays due to the reduced number of switching thin-film transistors. We also study theoretical calculation for high light extraction efficiency of LE-OFETs. Moreover, we believe that the development of LE-OFET surely lead to electrically driven organic lasers.