Dangling-bond defect state creation in microcrystalline silicon thin-film transistors

We analyze the threshold voltage shift in microcrystalline Si thin-film tra nsistors (TFTs), in terms of a recently developed thermalization energy con cept for dangling-bond defect state creation in amorphous Si TFTs. The rate of the threshold voltage shift in microcrystalline Si TFTs is much lower t han in amorphous Si TFTs, but the characteristic energy for the process. wh ich we identify as the mean energy to break a Si-Si bond, is virtually the same. This suggests that the same basic Si-Si bond breaking process is resp onsible for the threshold voltage shift in both cases. The lower magnitude in microcrystalline Si TFTs is due to a much lower attempt frequency far th e process. We interpret the attempt frequency in amorphous and microcrystal line silicon in terms of the localization length of the electron wave funct ion and the effect of stabilizing H atoms being located only at grain bound aries. (C) 2000 American Institute of Physics. [S0003-6951(00)03631-7].