Effect of dielectric surface passivation on organic field-effect transistors: spectral analysis of the density of trap-states

• Published in: Semiconductor science and technology 2022-01, Vol.37 (1), p.15015
• Main Authors: Yadav, Yogesh, Singh, Samarendra Pratap
• Format: Article
• Language: English
• Subjects: contact resistance; HMDS; OTS; PBTTT-C14; self assembled monolayer (SAM); trap-DOS
• ISSN: 0268-1242; 1361-6641
• DOI: 10.1088/1361-6641/ac3c97

The semiconductor/dielectric interface is arguably the most important region in field-effect transistors. This article investigates the performance-enhancing effects of passivation of the dielectric surface by a self-assembled layer (SAM) of silanes on organic field-effect transistors. Apart from conventional figures of merit for the devices, the energetic distribution of the density of the in-gap trap-states (trap-DOS) and the contact resistance are evaluated using numerical methods. The investigation reveals that the surface passivation of the dielectric SiO 2 has a dual effect on device operation. Firstly, it establishes quantitatively that the surface passivation leads to a significant reduction in the density of both shallow and deep traps in the organic semiconductor PBTTT-C14. This effect outweighs the impact of the SAM dipoles on the device turn-on. Secondly, the contact resistance gets lowered by a factor of more than 10 due to the improved top-surface morphology of the PBTTT-C14 thin film. The lower contact resistance in devices is corroborated by lower contact potential difference between PBTTT-C14 and gold, measured using scanning kelvin probe microscopy.