Piezotronics and piezo-phototronics based on<i>a</i>-axis nano/microwires: fundamentals and applications

One-dimensional semiconductors with wurtzite structure, such as GaN, ZnO and CdS nano/microwires, exhibit superior semiconductor, piezoelectric and mechanical properties, making them excellent candidates for novel electronic, opto-electronic devices and integrated systems. More importantly, the coupling between piezoelectric polarization and semiconductor properties (including electric transport and photoexcitation) gives rise to unique and unprecedented physical characteristics and has led to emerging fields of piezotronics and piezo-phototronics. On the basis of the extensive studies in c-axis semiconductor nano/microwires, piezotronics and piezo-phototronics based on a-axis nano/microwires have further been explored and demonstrated recently. We review both the fundamental progresses and developed applications of piezotronics and piezo-phototronics based on a-axis nano/microwires, which further improve the theoretical framework and expand the practical applications of piezotronics and piezo-phototronics in functional nanodevices and nanosystems.