Evolution of Nanocrystalline Silicon Layers Deposited at 150°C for Thin Film Transistor Channels

Thin film transistors of nanocrystalline silicon (nc-Si:H) are made in the staggered topgate, bottom-source/drain geometry. To achieve both high carrier mobility and low off current, the nc-Si:H channel material must be kept thin but comprise a contiguous 10-nm thick crystalline layer at its top. We study this electrically most interesting top layer of the nc-Si:H channel film by AFM and SEM. Introducing an nc-Si:H seed layer underneath the TFT promotes the structural evolution of the nc-Si:H channel layer and raises the electron field effect mobility up to 40 cm2V-1s-1.