On the Scaling of Zinc Oxide Thin-Film Transistors

Aug 31, 2020, 11:00 am12:30 pm
Zoom (https://princeton.zoom.us/j/92104113916)
Event Description


Large-Area Electronics (LAE) is a multi-billion-dollar industry at the core of the flat-panel display market. Fundamentally, it is a technology which uniquely merges dense microelectronics with meter-scale production, offering a one-of-a-kind form-factor over conventional microchip electronics (e.g. Silicon wafer based CMOS). In LAE, electronics are integrated on glass and plastic sheets, enabling not only large-area integration but also flexible, stretchable, and transparent electronics. Due to the compatibility of many sensors, optical-devices, and passive electronic components with LAE-technology, a large and novel application-space harnessing this variety of features is possible. This goes far beyond the display market, and includes energy harvesting and original sensing systems. However, the transistor technology based on thin-film transistors (TFTs) is severely limited in performance due to the poor semiconductor materials available in LAE. Consequently, pure LAE systems are difficult to realize, whereas a hybrid technology combining LAE with conventional CMOS technology introduces its own design challenges. It might be that this bottleneck has delayed the widespread growth of LAE beyond the display industry.

Recently, industry-standard TFT technology has improved by 10x utilizing metal-oxide based semiconductors which provide greater performance over older technologies. This work explores how even further improvements in TFT performance can be achieved by shrinking of device dimensions. We find that these “scaled” TFTs can operate at nearly 100x higher frequency than previously reported TFTs, enabling compatibility of LAE technology with radio-frequency communication. This potentially disruptive improvement in TFT design is demonstrated through the first-ever gigahertz LAE-based oscillators, and two novel systems based on these oscillators. A scalable RFID-reader array is demonstrated which can read commercial HF-RFID tags. Second, a gigahertz-frequency LAE-compatible phased array transmitter with beam-steering capability is showcased. All in all, scaling of TFTs can enable greater freedom and functionality in the design of LAE systems, hopefully bringing its unique offerings closer to becoming a reality.