External Schottky barrier diodes (SBD) are generally used to suppress the conduction of the body diode of MOSFET. A large external SBD is required for a high voltage module because of its high specific resistance, while the forward voltage of SBD should be kept smaller than the built-in potential of the body diode. Embedding SBD into MOSFET with short cycle length increases maximum source-drain voltage where body diode remains inactive, resulting in high current density of SBD current. We propose a MOSFET structure where an SBD is embedded into each unit cell and an additional doping is applied, which allows high current density in reverse operation without any activation of body diode. The proposed MOSFET was successfully fabricated and much higher reverse current density was demonstrated compared to the external SBD. We can expect to reduce total chip size of high voltage modules using the proposed MOSFET embedding SBD.
Information on localized states at the interfaces of solution-processed organic semiconductors and polymer gate insulators is critical to the development of printable organic field-effect transistors (OFETs) with good electrical performance. This paper reports on the use of impedance spectroscopy to determine the energy distribution of the density of interface states in organic metal-insulator-semiconductor (MIS) capacitors based on poly(3-hexylthiophene) (P3HT) with three different polymer gate insulators, including polyimide, poly(4-vinylphenol), and poly(methylsilsesquioxane). The findings of the study indicate that the impedance characteristics of the P3HT MIS capacitors are strongly affected by patterning and thermal annealing of the organic semiconductor films. To extract the interface-state distributions from the conductance of the P3HT MIS capacitors, an equivalent circuit model with continuum trap states is used, which also takes the band-bending fluctuations into consideration. In addition, the relationship between the determined interface states and the electrical characteristics of P3HT-based OFETs is investigated.
This work reports an SiC-MOSFET which replaces a part of the channel resistance with an additional embedded resistance, called a source resistance (Rs). MOSFETs with Rs have higher resistance during short circuit compared with MOSFETs without Rs and suppress short-circuit currents. An improvement of the trade-off relationship between short-circuit capability and on-resistance was obtained with MOSFETs including embedded Rs.
A trench gate SiC-MOSFET with BPW grounded by tilted Al implantation is developed in order to optimize the cell design and process for grounding the BPW in a more simple manner. From evaluation of static characteristics, the MOSFETs with sidewall region can improve the trade-off relationship between Ron,sp and Vbd by the variation of dSRs, and is superior than that of conventional BPW ground contact structure. From evaluation of dynamic characteristics, the MOSFETs with sidewall region can realize stable p-type ohmic contact for BPW compared with conventional BPW ground contact structure. Furthermore, the trade-off between Ron,sp and tsc of this device is adjusted to optimized layout of the p-type sidewall regions without degradation of the dV/dt dependence of turn-on and turn-off losses.
Solution-based organic field-effect transistors (OFETs) with low parasitic capacitance have been fabricated using a self-aligned method. The self-aligned processes using a cross-linking polymer gate insulator allow fabricating electrically stable polymer OFETs with small overlap area between the source-drain electrodes and the gate electrode, whose frequency characteristics have been investigated by impedance spectroscopy (IS). The IS of polymer OFETs with self-aligned electrodes reveals frequency-dependent channel formation process and the frequency response in FET structure. key words: organic field-effect transistors, frequency response, selfaligned method, impedance spectroscopy, cross-linking polymer insulators Hiroyoshi Naito received the B.E., M.E. and Dr.Eng. degrees from Osaka Prefecture University in 1979University in , 1981University in , and 1984 He is a Professor in the Department of Physics and Electronics, Osaka Prefecture University. He has been engaged in the photoelectric characterization of disordered semiconductors such as amorphous chalcogenide glasses and of liquid crystalline materials. His current interests are optical and electronic properties of organic semiconductors and their application to optoelectronic devices. Prof. Naito is a member of the Imaging
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