Piezotronics and piezo-phototronics – From single nanodevices to array of devices and then to integrated functional system

• Piezotronic effect utilizes strain-induced piezopotential as “gate” to tune/control charge carrier transport at a contact or junction.
• Piezo-phototronic effect uses piezopotential to control the carrier generation, transport, separation and/or recombination.
• Piezotronic effect is a universal effect which exists in nanowires and thin films of both n and p-type.
• Large-scale 3D vertical nanowire piezotronic transistors array has been implemented for active/adaptive sensing.
• Piezo-phototronic nanowire LED array has been fabricated for parallel electroluminescent imaging of pressure distribution.

SummaryDue to the polarization of ions in a crystal that has non-central symmetry in piezoelectric-semiconductors such as ZnO, GaN and InN, piezoelectric polarization charges are created at the interface region by applying a strain, which created a potential (piezopotential) in the crystal. Piezotronics is about the devices fabricated using the piezopotential as a “gate” voltage to tune/control charge carrier transport at a contact or junction. The piezo-phototronic effect is to use the piezopotential to control the carrier generation, transport, separation and/or recombination for improving the performance of optoelectronic devices, such as solar cell and LED. Starting from the fundamental physics principles, this article gives an updated review about the fabrication of array of piezotronic devices so that they can be integrated into a system for achieving specific functions as sensors and MEMS. This first demonstration of fabricating array of piezotronic devices and integrated them into a system is a major milestone in nanotechnology, and it represents one of the promising directions of nanoelectronics.

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