Contact Doping as a Design Strategy for Compact TFT-Based Temperature Sensing

Contact-controlled devices, such as source-gated transistors (SGTs), deliberately use energy barriers at the source, and naturally, the positive temperature dependence (PTD) of drain current can be utilized for temperature sensing. We exploit the difference in drain current activation energy, which arises with contact doping in polysilicon n-type contact-controlled transistors, to demonstrate output current with either a PTD or negative temperature dependence (NTD). The range over which output current varies linearly with temperature, as well as the sensitivity, can be tailored by the choice of reference current magnitude and relative source contact properties within the current mirror. The sensing scheme simplifies the circuit design because it relies solely on thin-film transistors and it has inherent immunity to output voltage variation. This ability to tune the sign of temperature dependence allows facile integration in applications requiring homeostasis via feedback, e.g., electronic skin, in a minimal layout area and potentially with convenient reduction of patterning steps during fabrication.