Effects of field dependent mobility and contact barriers on liquid crystalline phthalocyanine organic transistors

Copper phthalocyanine (CuPc) transistors were fabricated using the Langmuir-Blodgett technique to produce bottom contact organic field effect transistors (OFETs) on silicon substrates. The resultant devices were measured and the performance was analyzed using a two-dimensional numerical simulation of the device structure. A hole barrier at the Au/phthalocyanine source and drain contacts was seen from the experimental data. The numerical simulations were used to extract a barrier height of 0.415 eV at the Au/phthalocyanine contacts. Also, a Frenkel-Poole mobility model was used to account for the drain current in the transistors and a high field mobility of 0.018 cm ²/V sec was extracted from the experimental data. The resultant device parameters were compared to simple analytical results and the benefits of enhanced two-dimensional modeling of OFETs are shown.