Key Laboratory of Inorganic Functional Material and Device, CAS, Shanghai Institute of Ceramics, Chinese Academy of Sciences
中国科学院无机功能材料与器件重点实验室

　　Bistability of Hydrogen Impurity in ZnO under Light Illumination

　　Prof. Chul-Hong Park

　　Research Center for Dielectric and Advanced Matter Physics, Department of Physics Education,

　　Pusan National University

　　时间：2015年04月23日（星期四）上午09:00

　　地点： 4号楼14楼 第一会议室

　　联系人：曾江涛 副研究员

　　李国荣　研究员

　　欢迎各位老师同学光临!

　　Bistability of Hydrogen Impurity in ZnO under Light Illumination

　　Chul Hong Park

　　¹Research Center for Dielectric and Advanced Matter Physics, Pusan National University, Gumjung, Busan 609-735, Korea

　　Since ZnO-based oxide semiconductors are promising materials for transparent oxide electronics and blue LED, the oxides have been extensively investigated. The heavily n-type doping of ZnO is now intensively investigated for the application of the transparent conducting oxide for the solar cell. Hydrogen is an ubiquitous element, and in semiconductors, hydrogen-related problems have always been important subjects, since hydrogen shows complicated properties. Substitutional hydrogen at oxygen site (H_O) is well-known to be a robust source of n-type conductivity in ZnO, but a puzzling aspect is that the doping limit by hydrogen is only about 10¹⁸cm^-3, even if solubility limit is much higher.

　　There is another puzzling aspect in ZnO, which is persistent photo-conductivity (PPC) in Zn. Since the PPC is a source of the light-induced instability of ZnO-based active device in flat panel display, it prevents the wide applications of theZnO-based thin film transistor, andmany researches are now invested to prevent it, however up to now, there is no satisfactory theory about two puzzles. We report the bistability of H_O in ZnO through first-principles electronic structure calculations. We find that as Fermi level is close to conduction bands, the H_O can undergo a large lattice relaxation, through which a deep level can be induced, capturing electrons and the deep state can be transformed into shallow donor state by a photon absorption. We suggest that the bistability can give explanations to two puzzling aspects.

　　Ref) H-H Nahm, C. H. Park, Y-S Kim - Scientific reports,4, 412 (2014)