Time-Resolved X-ray Excited Optical Luminescence to Observe Increasing Anomalous Emission of ZnO and GaN Epitaxial Structures

Bi-Hsuan Lin^1*, Yu-Hao Wu¹, Tai-Sing Wu¹, Yung-Chi Wu², Xiao-Yun Li¹, Wei-Rein Liu¹, Mau-Tsu Tang¹, Wen-Feng Hsieh²

¹National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
²Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan

* Presenter:Bi-Hsuan Lin, email:bihsuan@nsrrc.org.tw

The hard X-ray excited optical luminescence (XEOL)¹ with nano-focused beam provides both excellent spatial resolution and high enough peak power density, which make XEOL mapping and luminescence dynamics study achievable. In this report, we observed not only anomalous near-band-edge (NBE) luminescence from the non-polar a-plane MgZnO/ZnO multiple quantum wells (MQWs), of which the emission intensity increases more than 10 times after X-ray irradiation, but also extremely long NBE decay time in time-resolved XEOL (TR-XEOL) with the hybrid bunch mode. Different from the well-known less than 1 ns NBE emission lifetime, the long decay time gradually decreases from 130 ns to 35 ns with increasing the X-ray irradiation time. Therefore, we attribute that the anomalous NBE luminescence to the excitation of Mg-related energy state by the high energy X-ray nanobeam to increase the NBE emission. This suggestion was further confirmed in the XEOL spectra of the Si-doped and Mg-doped c-plane GaN epi-films. Additionally, the capabilities and current status of TPS 23A X-ray nanoprobe beamline will also be reported.

References:
1. Bi-Hsuan Lin*, Yu-Hao Wu, Tai-Sing Wu, Yung-Chi Wu, Xiao-Yun Li, Wei-Rein Liu*, Mau-Tsu Tang, and Wen-Feng Hsieh, Appl. Phys. Lett. 115, 171903 (2019).

Keywords: XEOL, TR-XEOL, XAS, Nanoprobe, ZnO