Dependency of organic phototransistor properties on the dielectric layers

Organic phototransistors with pentacene semiconductor and Ta2O5 or polymethyl methacrylate (PMMA) dielectric layer have been investigated. It was found that the phototransistor properties strongly depend on the dielectric layer. Under a broadband light with 10mW∕cm2, the sensitivity of the Ta2O5 based transistor is much higher than that of the PMMA based transistor. For Ta2O5 based transistor, the photosensitivity (the ratio of photocurrent to dark current) and the threshold voltage shift are 4000 and 13.5V, respectively. While for PMMA based transistor, the corresponding values are only 0.5 and 2.9V, respectively. That large difference is attributed to the electron trapping ability of Ta2O5.

[1]  E. J. Rymaszewski,et al.  Study of electron trapping in the amorphous tantalum oxide thin films prepared by d.c. magnetron reactive sputtering , 1997 .

[2]  T. Tsukada,et al.  Amorphous silicon phototransistors , 1990 .

[3]  J. Salbeck,et al.  Organic phototransistor based on intramolecular charge transfer in a bifunctional spiro compound , 2004 .

[4]  D. Kim,et al.  High optical responsivity of InAlAs-InGaAs metamorphic high-electron mobility transistor on GaAs substrate with composite channels , 2003, IEEE Photonics Technology Letters.

[5]  Robert A. Street,et al.  Pentacene thin film transistors on inorganic dielectrics: Morphology, structural properties, and electronic transport , 2003 .

[6]  C. Dimitrakopoulos,et al.  Organic Thin Film Transistors for Large Area Electronics , 2002 .

[7]  S. Im,et al.  Correlation between photoelectric and optical absorption spectra of thermally evaporated pentacene films , 2004 .

[8]  S. Im,et al.  Fabrication of p-pentacene/n-Si organic photodiodes and characterization of their photoelectric properties , 2003 .

[9]  Gilles Horowitz,et al.  Organic thin film transistors: From theory to real devices , 2004 .

[10]  Stephen R. Forrest,et al.  Effects of film morphology and gate dielectric surface preparation on the electrical characteristics of organic-vapor-phase-deposited pentacene thin-film transistors , 2002 .

[11]  Yan Liang,et al.  Low-voltage pentacene thin-film transistors with Ta2O5 gate insulators and their reversible light-induced threshold voltage shift , 2005 .

[12]  Yong-Young Noh,et al.  High-photosensitivity p-channel organic phototransistors based on a biphenyl end-capped fused bithiophene oligomer , 2005 .

[13]  T. Jackson,et al.  Stacked pentacene layer organic thin-film transistors with improved characteristics , 1997, IEEE Electron Device Letters.

[14]  J. Kanicki,et al.  Thin-film organic polymer phototransistors , 2004, IEEE Transactions on Electron Devices.

[15]  Nitesh Kumar,et al.  Light responsive polymer field-effect transistor , 2001 .