Use of doping to achieve low contact resistance in bottom-gate top-contact type organic transistor with liquid-crystalline organic semiconductor, Ph-BTBT-10

Abstract

We have investigated the characteristics of bottom-gate and top-contact type field effect transistors fabricated with polycrystalline thin films of a liquid-crystalline organic semiconductor, 2-decyl-7-phenyl-benzothienobenzothiophene (Ph-BTBT-10), with a p-type dopant, tetrafluoro-tetracyano-quinodimethane (F4-TCNQ). We found that the contact resistance between the semiconductor and electrode was reduced from 3.0 kΩ cm to 1.2 kΩ cm by contact doping with F4-TCNQ, and to 0.9 kΩcm by subsequent thermal annealing of the films, in which the F4-TCNQ dopant diffused from the surface to the interior of the Ph-BTBT-10 thin film. In addition, we found that contact-doped and thermally annealed devices showed higher mobility and smaller threshold voltage in short-channel devices compared to pristine devices. We conclude that thermal diffusion of dopants to improve FET performance is an important technique.

Liquid crystalline self-assembly of azulene–thiophene hybrids and their applications as OFET materials

“…8(c)). 52 The sum of both contact resistances seems to be 1.8 MΩ cm. This is only a small proportion of the resistance of the transistor.…”

Recent advances in doped organic field-effect transistors: mechanism, influencing factors, materials, and development directions

“…Hiroaki Iino et al used the structure of BGTC to evaporate a layer of F4-TCNQ between Au electrodes and the liquid-crystal material 2-decyl-7-phenylbenzothiophene (Ph-BTBT-10). 111 The contact resistance of the devices was reduced by more than half (from 3.0 to 1.2 kΩ cm) through the contact doping of F4-TCNQ. The device achieved a higher mobility and lower threshold voltage due to the diffusion of dopants filling the deep wells in the organic semiconductor layer.…”

Solution‐Doped Donor–Acceptor Copolymers Based on Diketopyrrolopyrrole and 3, 3′‐Bis (2‐(2‐(2‐Methoxyethoxy) Ethoxy) ethoxy)‐2, 2′‐Bithiophene Exhibiting Outstanding Thermoelectric Power Factors with p‐Dopants

“…The increased mobility and more positive threshold voltages on doping indicate a decreased density of shallow trap defects, a decrease in trap states at grain boundaries, or a reduction in contact resistance. [87,88]…”