A study on pentacene organic thin-film transistor with different gate materials on various substrates

Bottom-gate pentacene organic thin-film transistors (OTFTs) with HfLaO gate dielectric have been fabricated on different substrates with different gate materials (namely, Ti- or Al-coated vacuum tape, n-Si wafer, and ITO-coated glass) and the effects of the gate material on device performance have been studied. Although the dielectric surface and pentacene grain on the Ti- and Al-coated vacuum tapes are much rougher and much smaller, respectively, than those on the n-Si wafer, the OTFTs fabricated on the two vacuum tapes have much higher carrier mobility than that fabricated on the n-Si wafer, implying that the gate material can greatly affect the device performance. Like the case for MOSFET, the possible reason is that metal gate can screen the remote phonon scattering of HfLaO and avoid the remote Coulomb scattering of silicon gate, thus resulting in higher carrier mobility for the OTFTs with Al and Ti gate electrodes. As a result, a high-performance OTFT with a carrier mobility of 4.95 cm²V^-1s^-1 and threshold voltage of -1.31 V was successfully fabricated on vacuum tape by using Ti gate.