Observation of channel formation carriers in pentacene field-effect transistor by electric field induced optical second harmonic generation (original) (raw)
Related papers
Probing of channel region in pentacene field effect transistor by optical second harmonic generation
Chemical Physics Letters, 2009
We studied the channel region at the gate insulator-active layer interface in pentacene field effect transistors (FETs) by using the electric field induced optical second harmonic generation (EFISHG) measurements. The SH signal was enhanced along the interface, dependent on biasing conditions, and reflected the region of accumulated holes that were injected from the source electrode. Analysing the charge accumulation condition along the channel, we explained the experimental EFISHG results.
Chemical Physics Letters, 2009
We studied the channel region at the gate insulator-active layer interface in pentacene field effect transistors (FETs) by using the electric field induced optical second harmonic generation (EFISHG) measurements. The SH signal was enhanced along the interface, dependent on biasing conditions, and reflected the region of accumulated holes that were injected from the source electrode. Analysing the charge accumulation condition along the channel, we explained the experimental EFISHG results.
Journal of Applied Physics, 2008
The injected carrier distribution in a pentacene field effect transistor ͑FET͒ was examined using optical second harmonic generation ͑SHG͒ measurements. Results showed that the SHG signal representing the profile of carriers injected from the source electrode distributed along the channel depends on the biasing conditions. The enhanced SHG around the drain electrode under the biasing condition u͓=͑V gs − V th ͒ / V ds ͔ Ͻ 1 was discussed based on the formation of an exhausted region of the distributed injected carriers. Organic FET ͑OFET͒ analysis, as a system of the Maxwell-Wagner ͑MW͒ effect element, suggests that injected carriers that are distributed along the pentacene-SiO 2 interface in the region between x =0 ͑source electrode͒ and x = uL ͑L: channel length͒ decrease the SHG intensity in this region. The SHG experiments with MW analysis described herein are helpful in understanding the performance of the OFET channel region.
Ieej Transactions on Fundamentals and Materials, 2007
To probe the carrier injection from Au source electrode into the channel of pentacene field effect transistors (FET), optical second harmonic generation (SHG) measurement is employed. SHG is enhanced at the off state due to Laplace electric field formation, whereas it is diminished at the on state. As the generation of SHG signal is in proportional to the electric field formed in the channel, we concluded that SHG measurement can probe the change of the electric field in the pentacene FET channel due to the injected and subsequently trapped holes.
Journal of Applied Physics, 2009
By probing optical second harmonic generation ͑SHG͒ signals enhanced around the injection electrode, the carrier injection mechanism of top-contact pentacene field-effect transistors ͑FETs͒ was investigated in terms of Schottky injection. At the Au source electrode, the SHG signal disappeared immediately after applying the driving voltage: the applied external electric field was cancelled by the space charge field formed by holes accumulated in the FET channel. At the Ag source electrode, the SH intensity decayed slowly. Its dependence on the device operation voltage suggested that the electric field was not relaxed by injected holes. The Schottky effect regulated carrier injection. The space charge field effect attributable to accumulated holes contributed to the carrier injection.
Origin of electric field distribution in organic field-effect transistor: Experiment and analysis
Journal of Applied Physics, 2009
Electric field distribution in the pentacene organic field-effect transistor ͑OFET͒ channel is investigated using the microscopic optical second-harmonic generation ͑SHG͒. At the on-and off-states of the OFET, enhanced SHG signal was observed near the drain electrode and at the source and drain electrodes. Our analytical analysis indicates that the Laplace field formation is in the off-state of the OFET. The electric field profile in the on-state representing distribution by the space-charge formation in the channel due to injected carriers was calculated by the transmission line model. Theoretical models are confirmed by the experimental results and the result shows that pentacene can be used as a dielectric material. On the basis of estimated potential distribution in the on-state, a model for the evaluation of the drain-source current is proposed.
Thin Solid Films, 2008
The pentacene field effect transistors (FETs)' operation for the injection carrier was revealed by means of the drain current-elapsed time (I ds-t) and optical second harmonic generation (SHG) measurements. The charge carriers forming the conducting channel of pentacene FETs were mainly holes injected from the Au source electrode. Carrier injection from source and drain electrodes was followed by the carrier trapping, and the SHG signal modulated by the change in the electric field distribution between Au the source and drain electrodes was shown. In particular, at the off state of the FET, electron injection and succeeding trapping were suggested. Furthermore, hole injection assisted by trapped electrons was also suggested.
Current Applied Physics, 2007
Carrier injection, carrier transport and carrier accumulation are three key process to understand the characteristics of organic field effect transistor (OFET) devices. In our previous studies, we showed the evidence of carrier injection from source electrode by means of optical second harmonic generation (SHG) measurement and capacitance-voltage (C-V) measurements, and explained the FET characteristics using a Maxwell-Wagner model. In this paper, to further clarify the behavior of the carrier transport and hole injection from source electrode, we focused on the hysteresis behavior observed in the current-voltage (I-V) and C-V characteristics of pentacene FETs. Employing the electric field induced SHG (EFISHG) and C-V measurements, we could show that the origin of the hysteresis behavior is caused by holes, which are injected and subsequently trapped in FET channel.
Japanese Journal of Applied Physics, 2012
The channel formation process in a pentacene field effect transistor was studied by directly probing the carrier motion along the channel in the time domain and the capacitance changes in the frequency domain. With the source and drain electrodes short circuited and the voltage applied only to the gate electrode, the carrier injection from both top electrodes and its motion along the channel was still observable, implying an interface charging process driven by a self-induced electric field. In addition, it was found that when the source and drain electrodes were short circuited, the capacitance of the device was larger than the geometric capacitance and proportional to the channel length, which also supported the interface charging model. The relationship between the two approaches was also discussed. #
Current Applied Physics, 2007
Pentacene field-effect transistor (FET) is analyzed as an injection-type element, assuming that carrier accumulation at the pentacenegate insulator is due to the Maxwell-Wagner effect. The FET characteristics are derived based on a model in which carriers injected from electrodes are accumulated at the interface, and they are then conveyed along the channel by the force of electric field formed between source and drain electrodes. Optical second harmonic generation from the channel is dependent on the off-and on-states of the FET channel, and suggesting that carriers injected from source electrode make a significant contribution to the space charge field formation.