Pulsed laser deposition of oxide gate dielectrics for pentacene organic field-effect transistors

We have fabricated Al2O3, LaAlO3 (LAO), CaHfO3 (CHO) and CaZrO3 (CZO) thin films for the dielectric layers of field-effect transistors (FETs) by pulsed laser deposition (PLD). The films exhibited very smooth surfaces with root-mean-squares (rms) roughnesses of ∼1.3 Å as evaluated by using atomic force microscopy (AFM). The breakdown electric fields of Al2O3, LAO, CHO and CZO films were 7, 6, 10 and 2 MV/cm, respectively. The magnitude of the leak current in each film was low enough to operate FET. We performed a comparative study of pentacene FET fabricated using these oxide dielectrics as gate insulators. High field-effect mobility of 1.4 cm2/V s and on/off current ratio of 107 were obtained in the pentacene FET using LAO gate insulating film. Use of the LAO films as gate dielectrics has been found to suppress the hysteresis of pentacene FET operations. The LAO films are relevant to the dielectric layer of organic FETs.