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

The effects of hafnium oxide (HfO
₂
) gate dielectric annealing treatment in oxygen (O
₂
) and ammonia (NH
₃
) ambient on the electrical performance of polymer thin-film transistors (PTFTs) based on poly(3-hexylthiophene) are investigated. The PTFTs with HfO
₂
gate 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 NH
₃
-annealed HfO
₂
shows higher carrier mobility, larger on/off current ratio, smaller subthreshold swing, and lower threshold voltage than the PTFT with O
₂
-annealed HfO
₂
. Capacitance-voltage analysis for metal-polymer-oxide-silicon structures indicates that the better electrical performance of the PTFT with NH
₃
-annealed HfO
₂
is attributed to improved dielectric/polymer interface and reduced series resistance in the transistor.