Drain Conductance Oscillations in Poly-Si Junctionless Nanowire Thin-Film Transistors

The drain conductance oscillations are simultaneously observed in the trigated and double-gated polySi junctionless (JL) nanowire thin-film transistors (TFTs). The strongest oscillations appear at V
_GS
of 1 V and V
_DS
of 4-5 V/6-7 V in 0.35-μm/5-μm poly-Si JL nanowire TFTs. To explain the drain conductance oscillations, in addition to the separated sub-bands and Coulomb blockade effect, the space-charge-potential barrier/grain boundary (GB) potential barrier in the channel and the kink effect in the output characteristics should be considered. The space-charge-potential barrier is affected by the unstable trapped electrons at GB and leads to the drain conductance oscillations. Due to the kink effect, an anomalous increase of the current in the output characteristics can enhance the conductance oscillations. Moreover, the channel of the double-gated device shows higher degree of crystallinity by solid-phase crystallization. Compared with the trigated device without solid-phase crystallization, less GB potential barriers in the channel of the double-gated device lead to a higher mobility in the channel, and these electrons can easily destroy the stability of the trapped electrons at the GBs, resulting in the stronger drain conductance oscillations. Therefore, the physical mechanisms are proposed to understand the drain conductance oscillations well in poly-Si JL nanowire TFTs.