Low-Operating-Voltage Polymer Thin-Film Transistors Based on Poly(3-Hexylthiophene) With Hafnium Oxide as the Gate Dielectric

The effects of hafnium oxide (HfO2) gate dielectric annealing treatment in oxygen (O2) and ammonia (NH3) ambient on the electrical performance of polymer thin-film transistors (PTFTs) based on poly(3-hexylthiophene) are investigated. The PTFTs with HfO2gate dielectric and also octadecyltrichlorosilane surface modification, prepared by spin-coating process, exhibit good performance, such as a small threshold voltage of -0.5 V and an operating voltage as low as -4 V. Results indicate that the PTFT with NH3-annealed HfO2shows higher carrier mobility, larger on/off current ratio, smaller subthreshold swing, and lower threshold voltage than the PTFT with O2-annealed HfO2. Capacitance-voltage analysis for metal-polymer-oxide-silicon structures indicates that the better electrical performance of the PTFT with NH3-annealed HfO2is attributed to improved dielectric/polymer interface and reduced series resistance in the transistor.