Fundamental Theory of Piezotronics

Abstract

Due to polarization of ions in crystals with noncentral symmetry, such as ZnO, GaN, and InN, a piezoelectric potential (piezopotential) is created in the crystal when stress is applied. Electronics fabricated using the inner-crystal piezopotential as a gate voltage to tune or control the charge transport behavior across a metal/semiconductor interface or a p-n junction are called piezotronics. This is different from the basic design of complimentary metal oxide semiconductor (CMOS) field-effect transistors and has applications in force and pressure triggered or controlled electronic devices, sensors, microelectromechanical systems (MEMS), human-computer interfacing, nanorobotics, and touch-pad technologies. Here, the theory of charge transport in piezotronic devices is investigated. In addition to presenting the formal theoretical frame work, analytical solutions are presented for cases including metal-semiconductor contact and p-n junctions under simplified conditions. Numerical calculations are given for predicting the current-voltage characteristics of a general piezotronic transistor: metal-ZnO nanowire-metal device. This study provides important insight into the working principles and characteristics of piezotronic devices, as well as providing guidance for device design.

An open-source platform to study uniaxial stress effects on nanoscale devices

“…19 The effect was interpreted as a modulation of the Schottky barrier height. 39 However, the method presented here allows a precise measurement of the contact resistance as the difference between the two-probe resistance, measured across the central InAs nanowire segment, and the four-probe resistance. The changes in contact resistance are negligible in our experiment, proving that the origin of the piezo-resistance in our experiment cannot to be attributed to changes in the Schottky barrier height.…”

“…As a consequence, the effect of strain on the electronic properties of the device is often dominated by Schottky contacts and by the influence that strain has on the barrier height through the piezo-electric effect. 39 In this work, we describe a measurement platform that enables the characterization of nanodevices by means of electrical transport and optical spectroscopy as a function of uniaxial stress. The platform relies on standard semiconductor fabrication methods to establish contact to nanostructures, and ultimately is able to reveal the effect large values of stress have on the transport properties of the device.…”

Effects of Piezoelectric Potential of ZnO on Resistive Switching Characteristics of Flexible ZnO/TiO2 Heterojunction Cells

“…The piezoelectric effect is the coupling of piezoelectric polarization (P pz ) and the intrinsic electric field, which can be used to tune charge transportation of corresponding materials. [6][7][8][9][10] Previous investigations have verified that the interfacial band structure can be tuned by the piezoelectric effect, [9][10][11][12] which is typically implemented via strain from mechanical deformation. The appropriate compression or tension to the piezoelectric material leads to a piezoelectric potential and thus causes redistribution of the free carrier in the heterostructures.…”

Comparative Study of Energy Harvesting from ZnO Nanorods Using Different Flexible Substrates

“…In recent years, various articles have been published on the piezoelectric properties of ZnO, but most of them have focused on hard substrates like GaN, glass, sapphire, ITO or Si (Wang and Song 2006;Wang et al 2007;Hu et al 2010;Chang et al 2011;Zhang, Liu, and Wang 2011). But one should keep in mind that, it is quite difficult to enhance the piezoelectric effect by transferring the mechanical energy into electrical energy using hard substrates (Hsu and Chen 2012).…”