Prof. Hyoungjeen Jeen (釜山大学校, 韓国) と 、東京大学 フウビン助教、幾原雄一教授との共同研究の成果が、米応用物理学誌 Applied Physics Lettersにオンライン掲載されました。JSPS二国間共同研究, 物質デバイス領域共同研究拠点, 人・環境と物質をつなぐイノベーション創出ダイナミック・アライアンス, 科研費新学術領域「ナノ構造情報」共同研究で得られた研究成果です。
Anup V. Sanchela*, Mian Wei, Haruki Zensyo, Bin Feng, Joonhyuk Lee, Gowoon Kim, Hyoungjeen Jeen, Yuichi Ikuhara, and Hiromichi Ohta*, “Large thickness dependence of the carrier mobility in a transparent oxide semiconductor, La-doped BaSnO3“, Appl. Phys. Lett. 112, 232102 (2018). (DOI: 10.1063/1.5033326)
After the discovery of high electron mobility (~320 cm2 V−1 s−1) in the La-doped BaSnO3 single crystal in 2012 by Kim et al., it has been attracted growing attention how to fabricate La-doped BaSnO3 thin films showing high electron mobility. Although many researchers have already discussed the way i.e. reducing the lattice mismatch between the film and the substrate to increase the mobility, the achievable mobility is still low, due to the lack of fundamental research such as thickness dependence.
We report herein that the carrier mobility of the 2%-La-doped BaSnO3 (LBSO) films on (001) SrTiO3 and (001) MgO substrates strongly depends on the thickness whereas it is unrelated to the lattice mismatch (+5.4 % for SrTiO3, −2.3 % for MgO). Although we observed large differences in the lattice parameters, the lateral grain size (~85 nm for SrTiO3, ~20 nm for MgO), the surface morphology and the density of misfit dislocations, the mobility increased almost simultaneously with the thickness in both cases and saturated at ~100 cm2 V−1 s−1, together with the approaching to the nominal carrier concentration (=[2 % La3+]), clearly indicating that the behavior of mobility depends on the film thickness. The present results would be beneficial to understand the behavior of mobility and fruitful to further enhance the mobility of LBSO films.
|Substrate||(001) SrTiO3||(001) MgO|
|Lattice mismatch||+5.4 %||−2.3 %|
|Lattice parameter||Increased with thickness||Decreased with thickness|
|Lateral grain size||~85 nm||~20 nm|
|Misfit dislocation||Every 7.3 nm||Not periodical manner|
|Electron transport||Both carrier concentration and mobility increased with thickness||<– Similar|