11:15 〜 11:30
▼ [19a-E201-6] Origin of Mobility Suppression in La-doped BaSnO3 Films (II)
キーワード：transparent oxide semiconductor, wide band gap semiconductor
As discussed in the part-I abstract, La-doped BaSnO3 (BLSO, Pm-3m, a=4.115 Å, Eg~3.1 eV) epitaxial films exhibit only ~100 cm2 V−1 s−1 though the single crystal exhibit very high mobility of 320 cm2 V−1 s−1.[1] The main origin of mobility suppression is considered to that doped La3+ ions were not activated at around the film/substrate interfaces. In order to clarify the origin of La3+ inactivation, we performed LAADF-STEM observations and EELS analyses (data not shown). We have clarified that oxygen concentration at around the BLSO film and substrate interface is lower than that in the bulk region. We have also detected 2+ valence state of Sn in the BLSO film by XAS. Since Sn2+ ions play not only as electron acceptor but also ionized impurity, mobility and carrier concentration suppression occurred simultaneously.
In order to minimize the oxygen deficiency at the heterointerface region, we fabricated BLSO (Ba0.98La0.02SnO3) epitaxial films by PLD under 10% ozone atmosphere. Figure summarizes (a) the carrier concentration (n), (b) thermopower and (c) Hall mobility (μHall) of the resultant films as a function of the BLSO thickness at room temperature. The n, S, and μHall dramatically increase in the thinner region (t<100 nm) and saturate ~2.6×1020 cm−3, −40 μV K−1, and ~115 cm2 V−1 s−1, respectively. Note that the obtained mobility (~115 cm2 V−1 s−1) is the highest value among the BLSO films grown by PLD.
Thus, we concluded from these results, oxygen off-stoichiometry at around the interface is the main origin of mobility suppression and the mobility can be improved by the film growth under highly oxidative condition. This conclusion is consistent with the fact that the BLSO films grown by MBE under oxygen plasma exhibited very high mobility.[2]
References
[1] H. J. Kim et al., APEX 5, 061102 (2012).
[2] H. Paik et al., APL Mater. 5, 116107 (2017).
In order to minimize the oxygen deficiency at the heterointerface region, we fabricated BLSO (Ba0.98La0.02SnO3) epitaxial films by PLD under 10% ozone atmosphere. Figure summarizes (a) the carrier concentration (n), (b) thermopower and (c) Hall mobility (μHall) of the resultant films as a function of the BLSO thickness at room temperature. The n, S, and μHall dramatically increase in the thinner region (t<100 nm) and saturate ~2.6×1020 cm−3, −40 μV K−1, and ~115 cm2 V−1 s−1, respectively. Note that the obtained mobility (~115 cm2 V−1 s−1) is the highest value among the BLSO films grown by PLD.
Thus, we concluded from these results, oxygen off-stoichiometry at around the interface is the main origin of mobility suppression and the mobility can be improved by the film growth under highly oxidative condition. This conclusion is consistent with the fact that the BLSO films grown by MBE under oxygen plasma exhibited very high mobility.[2]
References
[1] H. J. Kim et al., APEX 5, 061102 (2012).
[2] H. Paik et al., APL Mater. 5, 116107 (2017).