Nanocrystalline silicon thin-film transistors with 50-nm-thick deposited channel layer, 10 cm2V-1s-1 electron mobility and 108 on/off current ratio

Abstract.

Thin-film transistors were made using 50-nm-thick directly deposited nanocrystalline silicon channel layers. The transistors have a coplanar top gate structure. The nanocrystalline silicon was deposited from discharges in silane, hydrogen and silicon tetrafluoride. The transistors combine a high electron field effect mobility of ∼10 cm² V^-1s^-1 with a low ‘off’ current of ∼10^-14 A per μm of channel length and an ‘on’/‘off’ current ratio of ∼10⁸. This result shows that transistors made from directly deposited silicon can combine high mobility with low ‘off’ currents.