Biography：Zhong Lin Wang received the Ph.D. degree in physics from Arizona State University, Tempe, AZ, USA, in 1987.,He is currently the Hightower Chair in materials science and engineering, Regents’ Professor, Engineering Distinguished Professor, and Director with the Center for Nanostructure Characterization, Georgia Tech, Atlanta, GA, USA. He has made original and innovative contributions to the synthesis, discovery, characterization, and understanding of fundamental physical properties of oxide nanobelts and nanowires, as well as applications of nanowires in energy sciences, electronics, optoelectronics, and biological science. His discovery and breakthroughs in developing nanogenerators established the principle and technological road map for harvesting mechanical energy from environment and biological systems for powering personal electronics. His research on self-powered nanosystems has inspired the worldwide effort in academia and industry for studying energy for micro/nanosystems, which is currently a distinct disciplinary in energy research and future sensor networks. He coined and pioneered the field of piezotronics and piezophototronics by introducing piezoelectric potential gated charge transport process in fabricating new electronic and optoelectronic devices.

Piezotronics of the third- and fourth-generation semiconductors

Zhong Lin WANG

Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, 101400.

The classification of semiconductors is best given based on their crystallographic structures, which are the “DNA”s of general materials. The first generation semiconductors (Si, Ge) and the second generation semiconductors (GaAs) have a common characteristic that their crystal structures are cubic, so they exhibit the highest crystallographic symmetry. For the third generation semiconductors, such as GaN. SiC and ZnO, they have the hexagonal crystal structure. As for the fourth generation semiconductor such as Ga₂O₃, it has a monoclinic structure. Therefore, the non-centrosymmetric crystal structures at lower-symmetry for the third- and fourth-generation semiconductors make them distinctive different from the Si and GaAs owing to the piezoelectric effect that is generated by the polarization of ions in the crystal. A piezoelectric potential (piezopotential) is generated in the crystal by an externally applied strain. Electronics fabricated by using the inner-crystal piezopotential as a “gate” voltage to tune/control the charge transport behavior is named piezotronics, with applications in strain/force/pressure triggered/controlled electronic devices, sensors and logic units. Using the piezoelectric polarization charges at the pn junction to control charge carrier separation or combination process in optoelectronics is called the piezo-phototronic effect. This talk will focus on how to use piezo-phototronic effect to tune the efficiency of LED lighting and solar cells.  

L. Zhu and Z.L. Wang* “A perspective on piezotronics and piezo-phototronics based on the third and fourth generation semiconductors”, Appl. Phys. Lett. 122 (2023) 250501;

W.Z. Wu, X.N. Wen, Z.L. Wang “Pixel-addressable matrix of vertical-nanowire piezotronic transistors for active/adaptive tactile imaging”, Science, 340 (2013) 952-957.

C.F. Pan, L. Dong, G. Zhu, S. Niu, R.M. Yu, Q. Yang, Y. Liu, Z.L. Wang* “Micrometer-resolution electroluminescence parallel-imaging of pressure distribution using piezoelectric nanowire-LED array”, Nature Photonics, 7 (2013) 752-758.

Q. Yang, W.H. Wang, S. Xu and Z.L. Wang^* “Enhancing light emission of ZnO microwire-based diodes by piezo-phototronic effect”, Nano Letters, 11 (2011) 4012–4017.

Z.L. Wang, Y. Zhang and W. Hu “Piezotronics and Piezo-phototronics – Application to the third generation semiconductors” (2 ed.), Springer, 2023.

C. Pan^*, J. Zhai^* and Z.L. Wang^* “Piezotronics and piezo-phototronics of third generation semiconductor nanowires” (Review), Chemical Review, (2019) 119, 15, 9303-9359;