New amplification scheme enables manufacturers to build low-power, low-loss devices for communications, wireless sensors.
Researchers at the University of Central Florida have developed a novel, low-cost acoustoelectric (AE) amplification scheme that resolves the issues found in transistor-based amplifiers and existing AE amplification systems. All transistor-based amplifiers suffer from a decrease in optical power (gain) as the frequency increases, and though current AE amplification systems can provide greater gain-frequency, they have low operating efficiency and low electromechanical coupling.
In contrast, the UCF AE amplification mechanism operates more efficiently and offers higher gains as the frequency increases. Using lateralextensional thin-film piezoelectric-on-silicon (TPoS) resonant cavities, the invention amplifies bulk acoustic waves in a structure with high electromechanical coupling. As a result, the innovation enables transistor-less amplification at both lower and higher frequencies and non-reciprocal devices. Manufacturers can use the new scheme to build more cost-effective, low-power, low-loss devices for communications, wireless sensors, and the Internet of Things (IoT). Example acoustic devices include unilateral amplifiers, zero-loss filters, oscillators, and circuit-less, high-detection range wireless sensors.
The new UCF apparatus comprises a semiconductor layer and a thin piezoelectric layer (such as TpoS) deposited/bonded onto the semiconductor layer to form an acoustic cavity. Within the composite structure, the energy exchange between the propagating acoustic waves of the piezoelectric medium and the charge carriers in the semiconductor would normally lead to acoustoelectric loss. However, by pumping energy into the semiconductor layer to form an electric field across it, the velocity of the charge carriers exceeds that of the acoustic waves. As a result, the energy transfer reverses (from the charge carriers to the acoustic waves), effectively amplifying the acoustic waves, so that as the frequency of operation increases, the achievable gain also increases.
In one example setup, the thin piezoelectric layer consists of 1 μm (20 percent) of scandium doped aluminum nitride (Sc0.2Al0.8N), and the semiconductor layer comprises 2 μm of lightly doped n-type Si. Access pads inject DC current into the semiconductor layer to form an electric field in parallel with the direction of acoustic wave propagation in the semiconductor layer.
The research team is looking for partners to develop the technology further for commercialization.
Stage of Development
- Lower power consumption compared to conventional transistor-based amplifiers
- Small footprint, near-zero insertion loss
- Fabrication of new devices without using active circuit components
- Elimination of power-hungry semiconductor amplifiers in all RF device applications
- Low-power, low-loss devices for communications, wireless sensors, and the Internet of Things (IoT)
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