Hiroki Ohsawa

Self-aligned metal double-gate junctionless p-channel low-temperature polycrystalline-germanium thin-film transistor with thin germanium film on glass substrate

Low-temperature (LT) polycrystalline-germanium (poly-Ge) thin-film transistors (TFTs) are viable contenders for use in the backplanes of flat-panel displays and in systems-on-glass because of their superior electrical properties compared with silicon and oxide semiconductors. However, LT poly-Ge shows strong p-type characteristics. Therefore, it is not easy to reduce the leakage current using a single-gate structure such as a top-gate or bottom-gate structure. In this study, self-aligned planar metal double-gate p-channel junctionless LT poly-Ge TFTs are fabricated on a glass substrate using a 15-nm-thick solid-phase crystallized poly-Ge film and aluminum-induced lateral metallization source–drain regions (Al-LM-SD). A nominal field-effect mobility of 19 cm2 V−1 s−1 and an on/off ratio of 2 × 103 were obtained by optimizing the Al-LM-SD on a glass substrate through a simple, inexpensive LT process.

Evaluation of pH sensors using self-aligned four-terminal planar embedded metal double-gate low-temperature polycrystalline-silicon thin-film transistors on glass substrate

This study presents an evaluation of pH sensors using self-aligned four-terminal planar embedded metal double-gate low-temperature polycrystalline-silicon thin-film transistors (TFTs) on a glass substrate. The voltage variation due to a change in pH is read as the variation in threshold voltage of the TFTs by connecting a TFT control gate to a glass electrode. Our experimental results confirm that these TFTs can be successfully used as pH sensors.

Self-aligned metal double-gate junctionless p-channel low-temperature polycrystalline-germanium thin-film transistors with a thin germanium channel on a glass substrate

Polyaystalline-germanium (poly-Ge) thin-film transistors (TFTs) are good candidates for next-generation TFTs for use in the backplane of flat-panel displays (FPDs). This is due to their superior electrical properties compared to those of Si and oxide semiconductors. However, poly-Ge shows a strong p-type characteristic; thus, it is not easy to reduce the leakage current using a single-gate (SG) structure. In this study, self-aligned metal double-gate (MeDG) junctionless (JL) p-channel (p-ch) low-temperature (LT) poly-Ge TFTs were fabricated on a glass substrate using a 15-nm-thick solid phase crystallized (SPC) poly-Ge film. Additionally, SG JL p-ch LT poly-Ge TFTs with 15-nm-thick SPC poly-Ge films were fabricated as reference TFTs. The self-aligned MeDG JL p-ch LT poly-Ge TFT shows superior performance compared to that of SG JL p-ch LT poly-Ge TFT.

Controllability of self-aligned four-terminal planar embedded metal double-gate low-temperature polycrystalline-silicon thin-film transistors on glass substrate

Self-aligned four-terminal n-channel (n-ch) and p-channel (p-ch) planar embedded metal double-gate polycrystalline-silicon thin-film transistors (TFTs) were fabricated on a glass substrate at a low temperature of 550 °C. This device includes a metal top gate (TG) and a metal bottom gate (BG), which are used as the drive and control gates, or vice versa. The BG was embedded in a glass substrate, and a poly-Si channel with large lateral grains was fabricated using continuous-wave laser lateral crystallization. The threshold voltage modulations under various control gate voltages (γ = ΔVth/ΔVCG) were nearly equal to the theoretical predictions in both the n-ch and p-ch TFTs. By using this high controllability, an E/D inverter was fabricated, and successful operation at Vdd = 2.0 V was confirmed.