p-Type Nonpolar a-ZnO:N Thin Films on r-Sapphire Substrates Grown by Molecular Beam Epitaxy

• Published in: Journal of electronic materials 2020-08, Vol.49 (8), p.4474-4478
• Main Authors: Maekawa, Naoki, Nakayama, Hirotake, Yamane, Nobuaki, Irie, Koji, Abe, Tomoki, Kasada, Hirofumi, Ichino, Kunio, Akaiwa, Kazuaki
• Format: Article
• Language: English
• Subjects: 19th International Conference on II-VI Compounds and Related Materials; Annealing; Characterization and Evaluation of Materials; Chemistry and Materials Science; Electron diffraction; Electronics and Microelectronics; Epitaxial growth; Hall effect; High energy electrons; Instrumentation; Materials Science; Molecular beam epitaxy; Nitrogen; Optical and Electronic Materials; Photoluminescence; Sapphire; Solid State Physics; Substrates; Thin films; Topical Collection: 19th International Conference on II-VI Compounds; Zinc oxide; Zinc oxides
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-020-08034-9

We have grown nonpolar nitrogen (N) doped a -plane zinc oxide (ZnO) films on r -plane sapphire substrates in order to eliminate the self-polarization component in the growth direction, which decreases the doping efficiency of N acceptors. Nonpolar a -ZnO:N films were grown by plasma-assisted molecular beam epitaxy (PA-MBE) using Zn metal and a plasma source of O 2 and NO mixed gas. It was confirmed by reflection high-energy electron diffraction and x-ray diffraction that single phase a -plane ZnO:N films were grown on the r -plane sapphire substrates. After the PA-MBE growth, the post-annealing was performed in an oxygen atmosphere. Photoluminescence experiments showed donor–acceptor pair emissions increase with increasing the annealing temperature (≤ 700°C). AC magnetic field Hall effect measurements revealed that n -type conduction of the as-grown films clearly changed to the p -type at the annealing temperature of 650°C. The resistivity, hole concentration, and mobility were ρ  = 3.4 Ω cm, p  = 8.0 × 10 17  cm −3 , and μ  = 2.3 cm 2 /Vs, respectively.