Performance and stability of solution-based cadmium sulfide thin film transistors: Role of CdS cluster size and film composition

Improved carrier mobility and threshold voltage (V-T) stability in cadmium sulfide (CdS) thin film transistors (TFTs) were studied and attributed to larger grain clusters in thicker CdS films rather than individual crystallite size. Non-zero V-T shifts (similar to 200 mV) in thicker films are attributed to the presence of cadmium hydroxide [Cd(OH)(2)] at the dielectric/CdS interface resulting from the chemical bath deposition process used to deposit the CdS films. V-T and mobility analyses indicate that clusters of CdS grains have a larger impact on TFT performance and stability than the presence of impurities in the bulk of the CdS. TFTs using this fabrication method achieved mobilities of similar to 22 cm(2)/Vs with V-T of 7V and Delta V-T of <200 mV after testing. The maximum processing temperature is 100 degrees C which makes this process compatible with flexible substrates. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773184]