Tailoring the anisotropism of interface exciton emission in a-plane ZnO/Zn_1-xMg_xO multiple quantum wells by using ZnMgO buffered layer

Wei-Rein Liu^1*, Yung-Chi Wu², Hou-Ren Chen², Ja-Hon Lin³, Wen-Feng Hsieh²

¹National Synchrotron Radiation Research Center,, Hsinchu, Taiwan
²Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu, Taiwan
³Department of Electro-Optical Engineering, National Taipei University of Technology, Taipei, Taiwan

* Presenter:Wei-Rein Liu, email:liu.weirein@nsrrc.org.tw

Ten-period a-plane ZnO/Zn_1-xMg_xO (ZnO/ZnMgO) multiple quantum wells (MQWs) with different widths of Zn1−xMgxO barrier lay were grown by pulsed-laser deposition on ZnMgO buffered r-plane sapphire. By introducing ZnMgO buffer layer between sapphire substrate and MQWs, we found from XRD and TEM that four sets of (0002)-oriented MQWs nano-domains (NDs) are embedded in regular a-plane ZnO/ZnMgO MQWs with in-plane rotation from one another which are inclined by 27.6° towards the [11-20]-direction ZnO/ZnMgO MQWs. The polarization-dependent photoluminescence spectra reveal that two additional linear polarizations of surface-bound exciton emission with orienting at with respect to the regular a-plane MQWs are attributed to the generation of (0002)-oriented NDs. The existence of (0002)-oriented NDs is further confirmed by the phase-contrast atomic force microscopy to modulate the optical anisotropism of surface-bound exciton emission in a-plane nonpolar ZnO/ZnMgO MQWs that can be used for anisotropic photonic devices in the future.

Keywords: ZnO, non polar, multiple quantum wells, pulsed-laser deposition, anisotropism