Improved electrical stability of CdS thin film transistors through Hydrogen-based thermal treatments

Thin film transistors (TFTs) with a bottom-gate configuration were fabricated using a photolithography process with chemically bath deposited (CBD) cadmium sulfide (CdS) films as the active channel. Thermal annealing in hydrogen was used to improve electrical stability and performance of the resulting CdS TFTs. Hydrogen thermal treatments results in significant V _T instability (V _T shift) improvement while increasing the I _on/I _off ratio without degrading carrier mobility. It is demonstrated that after annealing V _T shift and I _on/I _off improves from 10 V to 4.6 V and from 10⁵ to 10 ⁹, respectively. Carrier mobility remains in the order of 14.5 cm² V s^-1. The reduced V _T shift and performance is attributed to a reduction in oxygen species in the CdS after hydrogen annealing, as evaluated by Fourier transform infrared spectroscopy (FTIR).