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

摘要

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