CdCl₂ treatment on chemically deposited CdS active layers in thin film transistors

In this work CdS layers were deposited by an ammonia-free chemical bath deposition process on SiO₂/p-Si substrates as active layers of thin film transistors (TFT). The electrical characteristics of the CdS-based TFT with different channel lengths were analyzed after thermal annealing in forming gas combined with previous immersion in CdCl₂ saturated solution. The annealing temperatures were 100, 200 and 300°C. To determine the effects of the CdCl₂ treatment on the device electrical parameters, devices with and without previous immersion in CdCl₂ were thermal annealed in forming gas and analyzed. The results show that the thermal annealing processes at 100 and 200 °C do not improve the electrical characteristics of the devices in both conditions. The annealing at 300 °C in both conditions improves noticeably the electrical performance of the devices attaining mobilities of the order of 5 cm²/Vs, threshold voltage in the range -1.5-10 V, swing voltage in the range of 1.65-9 V and I_on/I_off current ratio of the order 10³-10⁶.