Source-Drain Metal Contact Effects on Short Channel a-Si:H Thin Film Transistors

Short-channel hydrogenated amorphous silicon thin-film transistors have been fabricated by using electron-beam lithography with the shortest channel length of L=0.2 µm. As source-drain contacts, Cr or Al have been used. In the case of Cr-contact field-effect mobility, µFE, degradation for decreasing L has been observed, while the devices with Al-contacts show µFE around 0.7 cm2/V ·s independently of the channel length. This result is related to low parasitic resistance shown by our devices and attributed to the Al-diffusion in the source-drain contact regions. The calculated maximum operating frequency for the shortest channel devices is about 250 MHz