Experimental and Numerical Investigation of Contact Doping Effects in Dinaphthothienothiphene Thin‐Film Transistors

Abstract

SUMMARYContact doping effects in p‐channel dinaphthothienothiphene (DNTT) thin‐film transistors with a bottom‐gate, top‐contact configuration were investigated with both experimental and numerical approach. Characteristic variation in transistor parameters such as the gate threshold voltage and the field‐effect mobility for devices with various channel lengths was suppressed by the contact doping with tetrafluorotetracyanoquinodimethane (F4TCNQ) as an acceptor dopant. The gate‐voltage dependence of contact resistance and channel resistance was also evaluated separately to examine the contact doping effect in detail. In addition, device simulation considering a Schottky barrier at a metal/semiconductor interface successfully reproduced the experimental current–voltage characteristics by using a hole concentration of the active DNTT layer in the order of 1017 cm−3, which was estimated by capacitance–voltage measurement for a metal/insulator/semiconductor capacitor structure. This study suggests the importance of establishing both the carrier doping and carrier concentration measurements toward realizing practical applications of organic transistors.