Devices, circuits, and systems based on gigahertz large-area electronics for wireless applications

Jul 27, 2023, 1:30 pm2:30 pm
EQUAD J323 & Zoom (See abstract for link)



Event Description

Future wireless systems envision a large-scale deployment of densely distributed sensing nodes, and those nodes are preferably associated with physical objects such that the rich context information from those nodes can be utilized. This motivates wireless module with low power consumption for adequate operation lifetime and high spatial resolution for accurate node addressing. Large-area electronics (LAE) is a promising technology for this purpose due to its large-area and flex-compatibility, while today’s mainstream electronic technologies (e.g., Si-CMOS and III-V semiconductors) are adversely hindered by the limited achievable chip size and rigid form factor.

However, the conventional LAE devices can only be operated up to ~100 MHz due to the limitations introduced by the semiconductor quality and fabrication process, and such operation frequency is far away from the gigahertz (GHz) regime commonly used in wireless communication standards. In this work, co-design of device, circuit, and system enables GHz LAE for practical wireless applications.

First, this work develops high-performance LAE devices in GHz regime. In terms of active devices, this work demonstrates self-aligned zinc-oxide (ZnO) thin-film transistors (TFTs) with unity power gain frequency fMAX exceeding 3 GHz, which is among the highest for metal-oxide TFTs with large-area and flex-compatibility. In terms of passive devices, this work demonstrates flex-compatible large-area planar inductors with a record-high quality factor (Q factor) of up to 65 in the 2.4-GHz wireless band, which motivates resonant operation of devices towards the development of highly efficient flexible and conformal wireless systems.

Second, this work presents radio-frequency switches enabled by the resonant operation of ZnO TFTs and high Q-factor LAE inductors. These switches feature a high OFF-to-ON impedance ratio of ~48 in 2.4-GHz wireless band, and this is sufficient for effective signal switching at microwave frequencies for practical wireless systems.

Third, using these GHz LAE devices and circuits as building blocks, two LAE-based wireless systems operating in 2.4-GHz wireless band are demonstrated, including: (1) a passive backscattering tag with beamforming capability and zero static power; (2) a reconfigurable antenna with tunable directionality and operating frequency. These proof-of-concept prototypes validate LAE’s capabilities and advantages towards wireless systems for Internet of Things and 5G/6G applications.

Finally, pathways towards ZnO TFTs with higher operation frequency will be discussed as future works, including the optimization of TFT profile for overlap capacitance reduction and the optimization of TFT fabrication process for smaller feature size.

Zoom link:

Advisers: James Sturm & Naveen Verma