Koida Takashi, Kaneko Tetsuya, Shibata Hajime
Research Center for Photovoltaics, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, Umezono 1-1-1, Tsukuba, Ibaraki 305-8568, Japan.
School of Engineering, Tokai University, 4-1-1, Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan.
Materials (Basel). 2017 Feb 8;10(2):141. doi: 10.3390/ma10020141.
This study investigated carrier compensation induced by thermal annealing in sputtered ZnO:Al (Al₂O₃: 0.25, 0.5, 1.0, and 2.0 wt %) films. The films were post-annealed in a N₂ atmosphere at low (1 × 10 atm) and high (1 × 10 atm) oxygen partial pressures (). In ZnO:Al films with low Al contents (i.e., 0.25 wt %), the carrier density () began to decrease at annealing temperatures () of 600 °C at low . At higher and/or Al contents, values began to decrease significantly at lower (ca. 400 °C). In addition, Zn became desorbed from the films during heating in a high vacuum (i.e., <1 × 10⁷ Pa). These results suggest the following: (i) Zn interstitials and Zn vacancies are created in the ZnO lattice during post-annealing treatments, thereby leading to carrier compensation by acceptor-type Zn vacancies; (ii) The compensation behavior is significantly enhanced for ZnO:Al films with high Al contents.
