Recent Progress on Piezotronic and Piezo‐Phototronic Effects in III‐Group Nitride Devices and Applications

Abstract

Wurtzite-structured III-group nitrides, like GaN, InN, AlN, and their alloys, present both piezoelectric and semiconducting properties under straining owing to the polarization of ions in a crystal with non-central symmetry. The piezoelectric polarization charges are created at the interface when a strain is applied. As a result, a piezoelectric potential (piezopotential) is produced, which is used as a "gate" to tune/control the charge transport behavior across a metal/semiconductor interface or a p-n junction. This is called as piezotronic effect. A series of piezotronic devices and applications have been developed, such as piezotronic nanogenerators (NGs), piezotronic transistors, piezotronic logic devices, piezotronic electromechanical memories, piezotronic enhanced biochemical, and gas sensors and so on. With the flourished development of piezotronic effect, the piezo-phototronic effect, as the threeway coupling of piezoelectric polarization, semiconductor properties, and optical excitation, utilizes the piezopotential to modulate the energy band profile and control the carrier generation, transportation, separation, and/or recombination for improving performances of optoelectronic devices. This paper intends to provide an overview of the rapid progress in the emerging fields of piezotronics and piezo-phototronics, covering from the fundamental principles to devices and applications. This study will provide important insight into the potential applications of GaN based electronic/optoelectronic devices in sensing, active flexible/stretchable electronics/optoelectronics, energy harvesting, human-machine interfacing, biomedical diagnosis/therapy, and prosthetics. Figure 2. Piezopotential in wurtzite crystal. a) Atomic model of the wurtzite Àstructured ZnO. b) The piezopotential distributed along a ZnO NW under axial strain calculated by numerical methods. The growth direction of the NW is along the c-axis. (Reproduced with permission. [27]

Recent Progress in Piezo‐Phototronic Effect Enhanced Solar Cells

“…Recently, an increasing interest in piezotronics and piezo‐phototronics accompanied by novel physical science and unprecedented device applications has been sparked . A static force induced piezopotential in the wurtzite structured crystal has appeared due to the lack of central symmetry.…”

Piezotronics and piezo-phototronics with third-generation semiconductors

“…47 Knowledge gained through carrying out these fundamental explorations is expected to positively impact the design and development of related devices with enhanced performance and efficiency (e.g., high-electron-mobility transistors 48 and insulated-gate bipolar transistors), critical for societally pervasive technologies. 49,50 In addition to associated fundamental interests and technological potential, it is expected that research and development efforts on piezotronic, piezophototronic, and piezophotonic effects on third-generation semiconductors will also be advanced and boosted by the commercial feasibility and maturity of related technological processes in manufacturing and integrating these materials. 46…”

Innovation Strategy Selection Facilitates High-Performance Flexible Piezoelectric Sensors

“…Consequently, the current transport behavior reflects the mechanical deformation of piezoelectric materials under the applied force [18]. Accordingly, many piezotronic diodes and piezotronic transistors as strain/pressure sensors have been reported [19][20][21][22][23]. The first piezotronic field effect transistor based on a single ZnO nanowire was fabricated in 2006, which has a linear sensing ability when the applied force is around nanonewton [21].…”