[20p-E303-1~14] 13.2 Exploratory Materials, Physical Properties, Devices

▼ [20p-E303-5] Investigation of hydrogen states in semiconducting BaSi2 by muon spin rotation

〇(D)Zhihao Xu¹, Takuma Sato¹, Jumpei Nakamura², Akihiro Koda², koichiro Shimomura², Takashi Suemasu¹ (1.Univ. Tsukuba, 2.KEK)

Keywords:hydrogen

BaSi₂ has advantages over other solar cell materials from the viewpoints of a suitable band gap of 1.3 eV, a large absorption coefficient of 3 × 10⁴ cm^-1 at 1.5 eV, exceeding those of CIGS, and a large minority-carrier diffusion length of ca. 10 μm [1]. The electrically active defect levels of the order of 10¹³ cm^-3 were detected even in high-quality BaSi₂ films by deep-level transient spectroscopy, and they were considered to originate from Si vacancies (V_Si) in BaSi₂ [2]. According to the first-principle calculations by Kumar et al.[3] that V_Si is most likely to occur as point defects in BaSi₂. In the previous research, we passivated these V_Si using atomic H by radio-frequency (RF) plasma generator. The photoresponsivity of BaSi₂ passivated with atomic H is higher by one order of magnitude than the highest value previously reported, and the minority carrier lifetime was also improved to 14 μs, equivalent to its bulk carrier lifetime. These results show that atomic H is an effective method to passivate V_Si [4]. Motivated by such a major role of H in BaSi₂, we plan to clarify the physical and electronic structure of isolated H centers via their muonium (Mu) analog as performed in GaN [5]. This is the first time to apply muon spin rotation (μSR) measurement to BaSi₂.