The design and characteristics of a junctionless (JL) bulk FinFET were compared with the silicon-on-insulator (SOI) JL nanowire transistor (JNT) using 3-D quantum transport device simulation. The JL bulk FinFET exhibits a favorable ON/OFF current ratio and short-channel characteristics by reducing the effective channel thickness that is caused by the channel/substrate junction. The drain-induced barrier lowering and the subthreshold slope are about 40 mV and 73 mV/dec, respectively, with an ON/OFF current ratio of 10 5 at W = 10 nm. The JL bulk FinFET is less sensitive to the channel thickness than the SOI JNT. Furthermore, the threshold voltage V th of the JL bulk FinFET can be easily tuned by varying substrate doping concentration N sub . The modulation range of V th as N sub changes from 10 18 to 10 19 cm −3 , which is around 30%. Index Terms-Fin-shaped field-effect transistor (FinFET), junctionless (JL), 3-D simulation.

This letter demonstrates for the first time junctionless (JL) gate-all-around (GAA) poly-Si thin-film transistors (TFTs) with ultrathin channels (2 nm). The subthreshold swing is 61 mV/decade and the ON/OFF current ratio is close to 10 8 because of the excellent gate controllability and ultrathin channel. The JL-GAA TFTs have a low drain-induced barrier lowering value of 6 mV/V, indicating greater suppression of the shortchannel effect than in JL-planar TFTs. The cumulative distribution of electrical parameters in JL-GAA is small. Therefore, the proposed JL-GAA TFTs of excellent device characteristics along with simple fabrication are highly promising for future system-on-panel and system-on-chip applications.Index Terms-Gate-all-around (GAA), junctionless (JL), thin-film transistor, ultrathin channel.

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The multi-layer metals of Ni/AuGe/Pt/Au with a Pt diffusion barrier layer of ohmic contact to n-GaAs were studied. The surface morphology and ohmic contact resistivity of multi-layer metals were characterized, with and without the Pt diffusion barrier layer for comparison. The SEM and EDS measurements show the Pt diffusion barrier layer can block the interdiffusion of atoms in multi-layer metals, and improve the surface morphology. The TLM results show that the samples with a Pt diffusion barrier layer have uniform ohmic contact resistance, indicating that the Pt diffusion barrier layer can increase the repetition and uniformity of ohmic contact to n-GaAs, and improve the thermal stability and reliability of GaAs-based devices.