Single crystalline ZnO film is grown on GaN/sapphire (0001) substrate by molecular beam epitaxy. Ga₂O₃ is introduced into the ZnO/GaN heterostructure intentionally by oxygen-plasma pre-exposure on the GaN surface prior to ZnO growth. The crystalline orientation and interfacial microstructure are characterized by X-ray diffraction and transmission electron microscopy. X-ray diffraction analysis shows strong c-axis preferred orientation of the ZnO film. Cross-sectional transmission electron microscope images reveal that an additional phase is formed at the interface of ZnO/GaN. Through a comparison of diffraction patterns, we confirm that the interface layer is monoclinic Ga₂O₃ and the main epitaxial relationship should be \( (0001)_{ZnO} \parallel (001)_{Ga_2 O_3 } \parallel (0001)_{GaN} \) and \( [2 - 1 - 10]_{ZnO} \parallel [010]_{Ga_2 O_3 } \parallel [2 - 1 - 10]_{GaN} \).

中文翻译：

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在GaN /蓝宝石（0001）衬底上MBE生长的ZnO膜的微观结构研究

通过分子束外延在GaN /蓝宝石（0001）衬底上生长单晶ZnO膜。在ZnO生长之前，通过在GaN表面进行氧等离子体预曝光，有意将Ga ₂ O ₃引入ZnO / GaN异质结构。晶体取向和界面微观结构通过X射线衍射和透射电子显微镜表征。X射线衍射分析显示出ZnO膜的强c轴优选取向。横截面透射电子显微镜图像显示在ZnO / GaN的界面处形成了附加相。通过比较衍射图，我们确认界面层为单斜晶Ga ₂ O _3。 并且主要外延关系应为\（（0001）_ {ZnO} \ parallel（001）_ {Ga_2 O_3} \ parallel（0001）_ {GaN} \）和\（[2-1-10] _ {ZnO } \ parallel [010] _ {Ga_2 O_3} \ parallel [2-1-10] _ {GaN} \）。