C-V characteristics of piezotronic metal-insulator-semiconductor transistor

Ultra-Low-Power and Wide-Operating-Voltage-Window Capacitive Piezotronic Sensor through Coupling of Piezocharges and Depletion Widths for Tactile Sensing

The rapid growth of Artificial Intelligence and Internet of Things (AIoT) demands the development of ultra-low-power devices for future advanced technology. In this study, we introduce a capacitive piezotronic sensor specifically designed for tactile sensing, which enables an ultra-low-voltage operation at nearly 0 reading bias conditions with a consistent response within a wide voltage range. This sensor directly detects capacitance changes induced by piezocharges, reflecting perturbation of the effective depletion width, and ensures ultralow power capability by eliminating the necessity of turning on the Schottky diode for the first time. The dynamic response of the sensor demonstrates ultralow power capability and immunity to triboelectric interference, making it particularly suitable for tactile sensing applications in robotics, prosthetics, and wearables. This study provides valuable insights and design guidelines for future ultra-low-power thin-film-based capacitive piezotronic/piezophototronic devices for tactile sensing.

Fundamentals and Applications of ZnO-Nanowire-Based Piezotronics and Piezo-Phototronics

The piezotronic effect is a coupling effect of semiconductor and piezoelectric properties. The piezoelectric potential is used to adjust the p-n junction barrier width and Schottky barrier height to control carrier transportation. At present, it has been applied in the fields of sensors, human-machine interaction, and active flexible electronic devices. The piezo-phototronic effect is a three-field coupling effect of semiconductor, photoexcitation, and piezoelectric properties. The piezoelectric potential generated by the applied strain in the piezoelectric semiconductor controls the generation, transport, separation, and recombination of carriers at the metal-semiconductor contact or p-n junction interface, thereby improving optoelectronic devices performance, such as photodetectors, solar cells, and light-emitting diodes (LED). Since then, the piezotronics and piezo-phototronic effects have attracted vast research interest due to their ability to remarkably enhance the performance of electronic and optoelectronic devices. Meanwhile, ZnO has become an ideal material for studying the piezotronic and piezo-phototronic effects due to its simple preparation process and better biocompatibility. In this review, first, the preparation methods and structural characteristics of ZnO nanowires (NWs) with different doping types were summarized. Then, the theoretical basis of the piezotronic effect and its application in the fields of sensors, biochemistry, energy harvesting, and logic operations (based on piezoelectric transistors) were reviewed. Next, the piezo-phototronic effect in the performance of photodetectors, solar cells, and LEDs was also summarized and analyzed. In addition, modulation of the piezotronic and piezo-phototronic effects was compared and summarized for different materials, structural designs, performance characteristics, and working mechanisms' analysis. This comprehensive review provides fundamental theoretical and applied guidance for future research directions in piezotronics and piezo-phototronics for optoelectronic devices and energy harvesting.