11:00 AM - 11:15 AM
▼ [19a-C212-8] Ambipolar field-effect transistor with polycrystalline BP3T film prepared by vapor film deposition method
Keywords:organic transistor, ambipolar transistor
The ambipolar field-effect transistor is an interesting prospect for the compact CMOS and optoelectronic device, in which both holes and electrons can simultaneously transport. Recently, single-crystal 5,5”-bis(4-biphenylyl)-2,2’:5’2”-terthiophene (BP3T) FET was reported to exhibit the ambipolar characteristic and also the gain-narrowed light emission. The single crystal itself has low trap states concentration and the BP3T molecules orient standing in the crystal domain, suitable for the organic light-emitting transistor (OLET) and organic laser application. However, the utilization of the single crystal samples is not versatile - i.e., the crystal is selected once from many - and it is not easy to reproduce a similar device. Herein, we have alternatively studied an in-situ fabrication/characterization method of polycrystalline BP3T films for ambipolar FETs.
The polycrystalline BP3T films with a grain diameter range of 5-20 µm were grown onto SiO2/Si substrate by the vapor film deposition (VFD) method. The OLET device (shown in the inset of Fig. 1) was fabricated by asymmetric metal electrode deposition without breaking the vacuum of ~10-6 mbar, followed by in-situ FET measurements. The asymmetric electrodes of Ca and Au were introduced to balance the carrier injection into the active layer. The device illustrates the ambipolar characteristic, as shown in Fig. 1, with the mobilities of 0.003 cm2/Vs equivalently for both hole and electron in the saturation regime. The field-effect mobilities and the threshold voltage are compared for devices using CYTOP-coated and non-coated gate insulators. Moreover, the comparison between single-crystal, polycrystalline film and amorphous film will be presented.
The polycrystalline BP3T films with a grain diameter range of 5-20 µm were grown onto SiO2/Si substrate by the vapor film deposition (VFD) method. The OLET device (shown in the inset of Fig. 1) was fabricated by asymmetric metal electrode deposition without breaking the vacuum of ~10-6 mbar, followed by in-situ FET measurements. The asymmetric electrodes of Ca and Au were introduced to balance the carrier injection into the active layer. The device illustrates the ambipolar characteristic, as shown in Fig. 1, with the mobilities of 0.003 cm2/Vs equivalently for both hole and electron in the saturation regime. The field-effect mobilities and the threshold voltage are compared for devices using CYTOP-coated and non-coated gate insulators. Moreover, the comparison between single-crystal, polycrystalline film and amorphous film will be presented.