Abstract
Transparent electronic materials are increasingly in demand for a variety of optoelectronic applications, ranging from passive transparent conductive windows to active thin-film transistors. BaSnO is a semiconducting oxide with a large band gap of more than 3.1 eV. Recently, we discovered that BaSnO doped with a few percent of La exhibits an unusually high electrical mobility of at room temperature and superior thermal stability at high temperatures [H. J. Kim et al., Appl. Phys. Express 5, 061102 (2012)]. Following that paper, here, we report various physical properties of (Ba,La)SnO single crystals and epitaxial films including temperature-dependent transport and phonon properties, optical properties, and first-principles calculations. We find that almost doping-independent mobility of is realized in the single crystals in a broad doping range from to cm. Moreover, the conductivity of reached at the latter carrier density is comparable to the highest value previously reported in the transparent conducting oxides. We attribute the high mobility to several physical properties of (Ba,La)SnO: a small effective mass coming from the ideal Sn-O-Sn bonding in a cubic perovskite network, small disorder effects due to the doping away from the SnO octahedra, and reduced carrier scattering due to the high dielectric constant. The observation of the reduced mobility of in the epitaxial films is mainly attributed to additional carrier scattering due to dislocations and grain boundaries, which are presumably created by the lattice mismatch between the substrate SrTiO and (Ba,La)SnO. The main optical gap coming from the charge transfer from O 2 to Sn 5 bands in (Ba,La)SnO single crystals remained at about 3.33 eV, and the in-gap states only slightly increased, thus, maintaining optical transparency in the visible spectral region. Based on all these results, we suggest that the doped BaSnO system holds great potential for realizing all perovskite-based transparent high-temperature high-power functional devices as well as highly mobile two-dimensional electron gas via an interface control of heterostructured films.
- Received 29 June 2012
DOI:https://doi.org/10.1103/PhysRevB.86.165205
©2012 American Physical Society