Oxide Semiconductor Layer Doping for Stable TFT Electrical Characteristics

The patent applies different doping strategies to different regions of the semiconductor layer: the channel region is kept undoped or lightly doped to maintain high mobility and reduce oxygen vacancies, while the source and drain regions are heavily doped with elements like indium or gallium to achieve low resistance. This local differentiation resolves the contradiction by optimizing each region for its specific function.

The patent uses composite semiconductor structures combining metal oxide layers with other materials. Specifically, it employs a stacked structure of oxide semiconductor layers with varying compositions (e.g., In-Ga-Zn-O layers with different atomic ratios) to achieve both high mobility in the channel and stable electrical characteristics through controlled oxygen vacancy distribution across the composite structure.

The patent implements selective doping where only the source and drain regions are heavily doped with metal elements to achieve low resistance, while the channel region maintains low carrier density. This is achieved by controlling the doping process to affect specific regions, thereby resolving the contradiction between conductivity and carrier density control.

The semiconductor layer is segmented into functionally distinct regions (channel, source, drain) with different doping concentrations. The channel region uses a metal oxide composition optimized for high mobility with minimal doping, while source and drain regions use the same base material but with heavy doping of specific elements like indium, creating a segmented structure that satisfies both conductivity and carrier density requirements.