| AVS 60th International Symposium and Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS+TF-MoA |
| Session: | Plasma Deposition |
| Presenter: | K. Matsushima, Kyushu University, Japan |
| Authors: | K. Matsushima, Kyushu University, Japan R. Shimizu, Kyushu University, Japan D. Yamashita, Kyushu University, Japan G. Uchida, Kyushu University, Japan H. Seo, Kyushu University, Japan K. Kamataki, Kyushu University, Japan K. Koga, Kyushu University, Japan M. Shiratani, Kyushu University, Japan N. Itagaki, Kyushu University, Japan |
| Correspondent: | Click to Email |
Materials with tunable bandgap are required for optoelectronics applications such as photo detectors, solar cells, light emitting diodes, and so on. Recently we have developed a novel ZnO based semiconductor, ZnInON (ZION), with tunable bandgap from 1.6 eV to 3.3 eV, being fabricated by sputtering method [1]. ZION has wurtzite crystal structure and high absorption coefficient of 10-5 cm-1. Here we have studied effects of Ar partial pressure during the sputtering deposition on the crystal growth of ZION films by means of plasma parameter measurements and evaluation of film properties such as crystallinity and electrical properties. Furthermore, we have demonstrated two-dimensional growth of single crystalline ZION films.
First, 10-nm-thick ZnO buffer layers were fabricated on c-Al2O3 substrates via nitrogen mediated crystallization (NMC) in N2-Ar atmosphere at 700oC [2]. Then, 1-μm-thick ZnO templates were fabricated on the ZnO buffer layers by RF magnetron sputtering at 700oC in Ar-O2 atmosphere. Finally, epitaxial ZION films were fabricated on the ZnO templates by RF magnetron sputtering. For fabrication of ZION films, N2, O2 and Ar gasses were used. The total pressure was 0.28 Pa and the partial pressure of Ar was 0.04-0.17 Pa. The supplied RF power was 0.49-3.95 W/cm2 and the deposition temperature was 360oC. The ZION film thickness was 30-50 nm.
X-ray diffraction measurements show that the full width at half maximum (FWHM) of rocking curves from (002) plane for the ZION films are noticeably small of 0.09°, being independent of the partial pressure of Ar in the sputtering atmosphere. Hall-effect measurements using the Van Der Pauw configuration reveal that the carrier density of ZION films decreases from 1.1×1020 cm-3 to 3.7×1019 cm-3 and the electron mobility increases from 66 cm2/Vsec to 87 cm2/Vsec with decreasing the partial pressure of Ar from 0.17 Pa to 0.04 Pa. This is because electron temperature in the plasma increases with decreasing the partial pressure of Ar, and thus the dissociation of oxygen and nitrogen molecules is enhanced, which can suppress the lattice defects related to nitrogen and/or oxygen deficiencies. Moreover, two-dimensional crystal growth of ZION films was observed at a low Ar partial pressure of 0.04 Pa. These results show that Ar partial pressure in sputtering atmosphere is an important parameter to control the growth mode and to improve electrical properties of ZION films.
This work was partially supported by JSPS and PRESTO.
[1] N. Itagaki, et al., “Metal oxynitride semiconductor containing zinc”, U.S. Patent No. 8274078 (2008-04-23).
[2] N. Itagaki, et al., Appl. Phys. Express 4 (2011) 011101.