| AVS 56th International Symposium & Exhibition | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM-ThM |
| Session: | Oxide Semiconductors |
| Presenter: | W. Chen, National Dong Hwa University, Taiwan |
| Authors: | W. Chen, National Dong Hwa University, Taiwan Y. Chen, National Dong Hwa University, Taiwan J. Liang, National Dong Hwa University, Taiwan C. Lu, National Dong Hwa University, Taiwan |
| Correspondent: | Click to Email |
ZnO is a promising material used in short-wave optoelectronic devices such as light emitting diodes. However, one important issue that should be resolved beforehand is the fabrication of p-type ZnO film, which is difficult due to various intrinsic donor defects inside ZnO crystals such as zinc interstitials or oxygen vacancies. Nitrogen (N) has been considered to be an effective acceptor dopant to realize p-type ZnO. In this work, we prepared N-doped p-type zinc oxide thin films deposited on sapphire by metal organic chemical vapor deposition. We have successfully prepared high quality p-type ZnO film by changing VI/II ratio (O2 / DMZn flow ratio), and the p-type ZnO film can be fabricated reproducibility using this method. Dimethylzinc (DMZn) and N2O were used as zinc precursor and N dopant source. The growth temperature was in the range of 300-400°C and the chamber pressure was 100 Torr. The O2 flow rate is in the range 900-1100 sccm and DMZn carrier gas flow rate is in the range 2-10 sccm. We found ZnO film prepared using N2O only as O source show n-type. After 800°C under O2 ambient annealing for 1 hr, a few sample originally n-type became p-type. The p-type concentration is 1.4x1018 cm-3. XRD shows higher ZnO (002) peak intensity of the film after annealing than that before annealing. On the other hand, if we use O2 and N2O together as O source during ZnO growth, most films show p-type even before annealing. XRD spectrum and PL analysis suggest that appropriate oxygen flows can improve the quality of ZnO film to eliminate those excessive donor defects. Hall measurement shows that the resistance is 0.24 Ωcm and its corresponding hole concentration is 7.16x1018 cm-3. The N 1s peak in XPS spectra is located at 398.5 eV, which represent N–Zn bonds. The N–Zn bonds imply that N is located at O position in ZnO crystal and forms bond with Zn. NO is known as an acceptor defect in the ZnO film, so the presence of N-Zn bonds suggest the acceptor formation in the ZnO film. Since N2O is the only source for N, the formation of N–Zn bond suggests that using N2O in the process is helpful in p-type formation of ZnO films.