Postannealing effects on undoped BaSi2 evaporated films grown on Si substrates

• Published in: Japanese Journal of Applied Physics 2017-05, Vol.56 (5S1)
• Main Authors: Suhara, Takamichi, Murata, Koichi, Navabi, Aryan, Hara, Kosuke O., Nakagawa, Yoshihiko, Trinh, Cham Thi, Kurokawa, Yasuyoshi, Suemasu, Takashi, Wang, Kang L., Usami, Noritaka
• Format: Article
• Language: English
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.56.05DB05

Semiconducting BaSi2 is expected as an alternative material for solar cell application because of large absorption coefficients and a suitable bandgap for single-junction solar cells. In this study, the electrical properties of undoped BaSi2 films grown by a simple vacuum evaporation method are explored. The obtained results show that an undoped evaporated film is an n-type semiconductor with a high carrier density of ∼1019 cm−3 and exhibits a metallic behavior. The quality of BaSi2 films is significantly improved by postannealing at 1000 °C with surface covering to prevent oxidation. After annealing, the carrier density of BaSi2 films markedly decreases and the temperature dependence of carrier density changes from being metallic to being semiconducting. By comprehensive structural analysis, it is speculated that postannealing improves the film quality, for example, by decreasing the density of grain boundaries.