A NEW DESIGN OF VERTICAL THIN FILM TRANSISTORS FOR HIGHLY FLEXIBLE ELECTRONICS AND ELECTRONIC SKIN
Abstract
Flexible thin-film transistors (TFTs) are of central importance for diverse electronic and particularly macroelectronic applications. The current TFTs using organic or inorganic thin film semiconductors are usually limited by either poor electrical performance or insufficient mechanical flexibility. Here we propose a new design of highly flexible vertical TFTs (VTFTs) with superior electrical performance and mechanical robustness. By using the graphene as a work-function tunable contact for semiconductor thin films, the vertical current flow across the graphene-semiconductor junction can be effectively modulated by an external gate potential to enable VTFTs with a high on-off ratio. The concept of VTFTs can offer several combined advantages not readily possible in conventional planar TFTs. First, with the design of graphene-semiconductor heterostructure based VTFTs, the ultra-short channel transistors (typically <100 nm as determined by the thickness of the semiconductor thin film rather than by lithography) can be readily created by using low resolution lithography to afford a delivering current greatly exceeding that of the conventional planar TFTs. Second, the vertical (out-of-plane) charge transport across the large area vertical junction makes the source-drain current much less affected by the in-plane cracks in the semiconductor thin films to afford unprecedented tolerance to in-plane cracks. The unique vertical transistor architecture can therefore enable ultra-short channel devices with very high delivering current and exceptional mechanical flexibility. Within this proposal, we will evaluate and optimize the frequency response of such VTFTs by exploring different semiconductor thin films with variable band offset and/or film thickness, with a goal to demonstrate 10-GHz transistors/circuits using 10-?m resolution lithography; we will develop solution processable VTFTs for highly flexible integrated electronics over large area plastic substrate; and we will further develop a conductive micro-structure air gap dielectric to integrate with the VTFTs for the creation of highly sensitive electronic skin for static and dynamic pressure mapping/tracking. The unique design of VTFTs simultaneously addresses two most critical challenges (low delivering current and insufficient mechanical flexibility) of conventional planar inorganic TFTs and can enable a new generation highly flexible electronics with exceptional electrical performance and mechanical robustness. The device structure and the fabrication approach is intrinsically scalable and can be readily extended to a wide range of semiconductor thin films, including the solution processable ones, to enable a low-temperature, low cost process to high performance VTFTs on a plastic substrate. It can therefore define a new pathway to high performance macroelectronics, and impact broad areas of existing applications and enable a wide array of flexible, wearable, degradable or disposable electronic systems for computing, sensing/monitoring, communication, storage, displays, and more. The integration of the VTFTs with unique conductive microstructure air gap dielectric can enable a new generational electronic skin with unprecedented sensitivity, flexibility and robustness.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512368
Entities
People
- Xiangfeng Duan
Organizations
- Office of Naval Research
- United States Navy
- University of California, Los Angeles