Stability of fully deuterated amorphous silicon thin-film transistors

The threshold voltage stability of fully deuterated (a-Si:D) and hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) is compared. The difference in the kinetic energy of D+ and H+ ions upon impact with the growing surface during radio-frequency plasma-enhanced chemical vapor deposition leads to material having different physical properties for the same nominal deposition conditions. However, a-Si:D and a-Si:H grown at the same growth rate by adjusting the gas pressure have almost identical properties. By using the growth rate as a normalizing parameter for comparing a-Si:H and a-Si:D TFTs, it is shown that there is no difference in the stability of a-Si:D compared with a-Si:H TFTs. This study rules out the possibility of a giant isotopic effect in amorphous silicon TFTs, and supports the model for Si dangling bond defect creation in a-Si:H where the breaking of weak Si–Si bonds is the rate-limiting step.