Photo-Induced Instability of Nanocrystalline Silicon TFTs

We examine the instability behavior of nanocrystalline silicon (nc-Si) thin-film transistors (TFTs) in the presence of electrical and optical stress. The change in threshold voltage and sub-threshold slope is more significant under combined bias-and-light stress when compared to bias stress alone. The threshold voltage shift after 6 h of bias stress is about 7 times larger in the case with illumination than in the dark. Under bias stress alone, the primary instability mechanism is charge trapping at the semiconductor/insulator interface. In contrast, under combined bias-and-light stress, the prevailing mechanism appears to be the creation of defect states in the channel, and believed to take place in the amorphous phase, where the increase in the electron density induced by electrical bias enhances the non-radiative recombination of photo-excited electron-hole pairs. The results reported here are consistent with observations of photo-induced efficiency degradation in solar cells.

[1]  R. Street,et al.  Hydrogenated amorphous silicon: Index , 1991 .

[2]  Arokia Nathan,et al.  Stability of nanocrystalline silicon bottom-gate thin film transistors with silicon nitride gate dielectric , 2007 .

[3]  S. Guha,et al.  Material structure and metastability of hydrogenated nanocrystalline silicon solar cells , 2006 .

[4]  Tsai,et al.  Light-induced metastable defects in hydrogenated amorphous silicon: A systematic study. , 1985, Physical review. B, Condensed matter.

[5]  Arokia Nathan,et al.  Low-Temperature Materials and Thin Film Transistors for Flexible Electronics , 2005, Proceedings of the IEEE.

[6]  Arokia Nathan,et al.  Light-induced metastability in thin nanocrystalline silicon films , 2009 .

[7]  Jackson,et al.  Stretched-exponential relaxation arising from dispersive diffusion of hydrogen in amorphous silicon. , 1987, Physical review letters.

[8]  A. Nathan,et al.  Absence of defect state creation in nanocrystalline silicon thin film transistors deduced from constant current stress measurements , 2007 .

[9]  M. J. Powell,et al.  Dangling-bond defect state creation in microcrystalline silicon thin-film transistors , 2000 .

[10]  Subhendu Guha,et al.  Light-induced metastability in hydrogenated nanocrystalline silicon solar cells , 2004 .

[11]  P. Tzanetakis,et al.  Comparison of Experiment and Theory of the Photoconductivity of a-Si:H up to a Generation Rate of 10 28 cm −3 s −1 , 1996 .

[12]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[13]  F. Liu,et al.  Transport mechanism of microcrystalline silicon thin films , 2002 .

[14]  J. Robertson,et al.  Directly deposited nanocrystalline silicon thin-film transistors with ultra high mobilities , 2006 .

[15]  Regis Vanderhaghen,et al.  Stable microcrystalline silicon thin-film transistors produced by the layer-by-layer technique , 1999 .

[16]  Andrew G. Glen,et al.  APPL , 2001 .

[17]  M. J. Powell.  The physics of amorphous-silicon thin-film transistors , 1989 .