Effect of Electrode Materials on the Electrical Characteristics of Amorphous Indium-Tin-Gallium-Zinc Oxide Thin-Film Transistors

In this study, we investigated the effect of electrode materials on the electrical characteristics of coplanar top-gate a-ITGZO thin-film transistors, in which the gate, source, and drain electrodes were made of the same metal, Ti or Al. The field-effect mobilities of the a-ITGZO thin-film transistors with Ti and Al electrodes were 35.2 and 20.1 cm2/V·s, respectively, and the threshold voltage of the a-ITGZO thin-film transistor with Ti electrodes was −0.4 V, whereas that of the transistor with Al electrodes was −1.8; this shift is attributed to the fact that Ti has a higher work function than Al. When Ti was used as the source and drain electrode material, the channel resistance and effective channel length were reduced owing to the penetration of metal atoms into the channel region from the edge of the source/drain electrodes.

Unidirectional Operation of p-GaN Gate AlGaN/GaN Heterojunction FET Using Rectifying Drain Electrode

In this study, we proposed a rectifying drain electrode that was embedded in a p-GaN gate AlGaN/GaN heterojunction field-effect transistor to achieve the unidirectional switching characteristics, without the need for a separate reverse blocking device or an additional process step. The rectifying drain electrode was implemented while using an embedded p-GaN gating electrode that was placed in front of the ohmic drain electrode. The embedded p-GaN gating electrode and the ohmic drain electrode are electrically shorted to each other. The concept was validated by technology computer aided design (TCAD) simulation along with an equivalent circuit, and the proposed device was demonstrated experimentally. The fabricated device exhibited the unidirectional characteristics successfully, with a threshold voltage of ~2 V, a maximum current density of ~100 mA/mm, and a forward drain turn-on voltage of ~2 V.

ESD Design and Analysis by Drain Electrode-Embedded Horizontal Schottky Elements for HV nLDMOSs

Electrostatic discharge (ESD) events can severely damage miniature components. Therefore, ESD protection is critical in integrated circuits. In this study, drain-electrode-embedded horizontal Schottky diode contact modulation and Schottky length reduction modulation were performed on a high-voltage 60-V n-channel laterally diffused metal-oxide–semiconductor transistor (nLDMOS) element. The effect of the on-voltage characteristics of cascade Schottky diodes on ESD protection was investigated. By using a transmission-line pulse tester, the trigger voltage, holding voltage, and secondary breakdown current (It2) of the nLDMOS element were determined using the I–V characteristic. As the N+ area was gradually replaced by the parasitic Schottky area at the drain electrode, an equivalent circuit of series Schottky diodes formed, which increased the on-resistance. The larger the Schottky area was the higher the It2 value was. This characteristic can considerably improve the ESD immunity of nLDMOS components (highest improvement of 104%). This is a good strategy for improving ESD reliability without increasing the production steps and fabrication cost.