[6p-C17-1~15] 21.1 Joint Session K "Wide bandgap oxide semiconductor materials and devices"

▼ [6p-C17-8] High mobility in amorphous ZnO_xS_y thin films

〇Yuting Zhu¹, Takanori Yamazaki¹, Yasushi Hirose^1,2, Shoichiro Nakao^1,2, Tetsuya Hasegawa^1,2 (1.Univ. of Tokyo, 2.KAST)

Keywords:amorphous oxide semiconductor, wide gap semiconductor, mixed anion semiconductor

Amorphous oxide semiconductors (AOSs) have been extensively studied because of their high electron mobility. Conventionally, AOSs are alloys of metal oxides of which conduction band minima (CBM) consist of metal s-orbitals. Recently, very high mobility over 100 cm²V^–1s^–1 was reported in a mixed-anion compound, ZnO_xN_y. Although the origin of high mobility has not been fully understood, one hypothesis is that CBM of ZnO_xN_y is spatially more homogeneous than conventional AOSs because it is composed of only Zn 4s-orbital. This hypothesis suggests high mobility in other amorphous mixed-anion compounds such as oxyfluoride and oxysulfide. In this study, we fabricated amorphous ZnO_xS_y thin films and investigated their electrical transport properties.
We tried alternate deposition of ZnS and ZnO targets under vacuum, and succeeded in obtaining ZnO_xS_y over the whole anion range. We found that while the end members, ZnS and ZnO were crystalized, their alloys became amorphous in a wide range under low laser fluence conditions. The resistivity of the amorphous ZnO_xS_y films increased with increase of S content or decrease of laser fluence. The films fabricated with higher laser fluence showed larger electron concentration N_e probably due to introduction of oxygen vacancies. Hall mobility μ_H vs Ne plot showed that the μ_H of the amorphous ZnO_xS_y films reached to 10-15 cm²V^–1s^–1. These results indicate that amorphous ZnO_xS_y is a promising amorphous semiconductor.