Low-operating-voltage polymer thin-film transistors based on poly(3-hexylthiophene) with hafnium oxide as the gate dielectric

Abstract

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}$. Capacitancevoltage 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. © 2006 IEEE.