Transparent electronic materials are increasingly in demand for a variety of optoelectronic applications, ranging from passive transparent conductive windows to active thin film transistors. suggest that the doped BaSnO 3 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 interface control of heterostructured films.

Transparent conducting oxides (TCOs) and transparent oxide semiconductors (TOSs) have become necessary materials for a variety of applications in the information and energy technologies, ranging from transparent electrodes to active electronics components. Perovskite barium stannate (BaSnO 3 ), a new TCO or TOS system, is a potential platform for realizing optoelectronic devices and observing novel electronic quantum states due to its high electron mobility, excellent thermal stability, high transparency, structural versatility, and flexible doping controllability. This article reviews recent progress in the doped BaSnO 3 system, discussing the wide physical properties, electron-scattering mechanism, and demonstration of key semiconducting devices such as pn diodes and field-effect transistors. Moreover, we discuss the pathways to achieving two-dimensional electron gases at the interface between BaSnO 3 and other perovskite oxides and describe remaining challenges for observing novel quantum phenomena at the heterointerface. 17.1

It was recently discovered that a transparent n-type (Ba,La)SnO 3 system has electrical mobility as high as 320 cm 2 V −1 s −1 at room temperature and superior thermal stability up to ∼500 • C. To understand comparatively the carrier-scattering mechanism in the doped BaSnO 3 , we investigate the physical properties of the single crystals of BaSn 1-x Sb x O 3 (x = 0.03, 0.05, and 0.10), which also show the n-type characters via the Sn site doping by Sb. Transmittance of the grown single crystals in the visible spectral region turn out to be similar to that of the (Ba,La)SnO 3 system, maintaining optical transparency. Temperature-dependent Hall effect measurements reveal that the electrical mobility at room temperature reaches as high as 79.4 cm 2 V −1 s −1 at a carrier density of 1.02 × 10 20 cm −3 , and upon increasing carrier density further, it systematically decreases nearly proportional to the inverse of the carrier density. The overall reduced mobility of the Ba(Sn,Sb)O 3 system as compared to the (Ba,La)SnO 3 system is attributed to the enhanced scattering caused by the Sb ions located in the direct conduction path. Based on the inverse proportionality between the carrier density and the electrical mobility, we suggest that the neutral impurity scattering becomes particularly strong in the Ba(Sn,Sb)O 3 .

We report the growth of Ba1−xLaxSnO3 (x = 0.00, 0.005, 0.01, 0.02, and 0.04) thin films on the insulating BaSnO3(001) substrate by pulsed laser deposition. The insulating BaSnO3 substrates were grown by the Cu2O-CuO flux, in which the molar fraction of KClO4 was systematically increased to reduce electron carriers and thus induce a doping induced metal-insulator transition, exhibiting a resistivity increase from ∼10−3 to ∼1012 Ω cm at room temperature. We find that all the Ba1−xLaxSnO3 films are epitaxial, showing good in-plane lattice matching with the substrate as confirmed by X-ray reciprocal space mappings and transmission electron microscopy studies. The Ba1−xLaxSnO3 (x = 0.005–0.04) films showed degenerate semiconducting behavior, and the electron mobility at room temperature reached 100 and 85 cm2 V−1 s−1 at doping levels 1.3 × 1020 and 6.8 × 1019 cm−3, respectively. This work demonstrates that thin perovskite stannate films of high quality can be grown on the BaSnO3(001) substrates for potential applications in transparent electronic devices.

Transparent p-CuI/n-BaSnO heterojunction diodes were successfully fabricated by the thermal evaporation of a (1 1 1) oriented γ-phase CuI film on top of an epitaxial BaSnO (0 0 1) film grown by the pulsed laser deposition. Upon the thickness of the CuI film being increased from 30 to 400 nm, the hole carrier density was systematically reduced from 6.0  ×  10 to 1.0  ×  10 cm and the corresponding rectification ratio of the pn diode was proportionally enhanced from ~10 to ~10. An energy band diagram exhibiting the type-II band alignment is proposed to describe the behavior of the heterojunction diode. A shift of a built-in potential caused by the hole carrier density change in the CuI film is attributed to the thickness-dependent rectification ratio. The best performing p-CuI/n-BaSnO diode exhibited a high current rectification ratio of 6.75  ×  10 at  ±2 V and an ideality factor of ~1.5.