Absence of enhanced stability in fully deuterated amorphous silicon thin-film transistors

The stability of fully deuterated amorphous silicon (a-Si:D) thin-film transistors is compared with their hydrogenated equivalent (a-Si:H) in terms of gate bias stress. The amorphous silicon channel and silicon nitride gate insulator layers were deposited by radio-frequency plasma-enhanced chemical-vapor deposition. The use of SiD4 rather than SiH4 for the deposition of a-Si:D changes the physical properties of the plasma given the same conditions of rf power, pressure, and gas flow rates. Consequently, a higher gas pressure is required to produce a-Si:D at the same growth rate and with similar bulk properties as a-Si:H. It is shown that a-Si:H and a-Si:D deposited at the same growth rate have very similar structural properties. Therefore transistors deposited at the same growth rate may be more sensibly compared to determine the effect of replacing H with D in amorphous silicon without significantly changing the silicon continuous random network. Using this criterion for comparison, no detectable differe...