Search

Materials that blend physical properties that are usually mutually exclusive could facilitate devices with novel functionalities. For example, the doped perovskite alkaline earth stannates BaSnO3 and SrSnO3 show the intriguing combination of high light transparency and high electrical conductivity. Understanding such emergent physics requires deep insight into the materials' electronic structures. Moreover, the band structure at the surfaces of those materials can deviate significantly from their bulk counterparts, thereby unlocking novel physical phenomena. Employing angle-resolved photoemission spectroscopy and ab initio calculations, we reveal the existence of a 2-dimensional metallic state at the SnO2-terminated surface of 1% La-doped BaSnO3 thin films. The observed surface state is characterized by a distinct carrier density and a lower effective mass compared to the bulk conduction band, of about 0.12me. These particular surface state properties place BaSnO3 among the materials suitable for engineering highly conductive transition metal oxide heterostructures. Transparent conductive oxides are wide bandgap conductors that combine weak optical absorption. Here, the authors report a two-dimensional electronic state on the surface of La-BaSnO3 and study its properties using a combination of electronic structure measurements and DFT calculations. [ABSTRACT FROM AUTHOR]

The discovery and development of ultra-wide bandgap (UWBG) semiconductors is crucial to accelerate the adoption of renewable power sources. This necessitates an UWBG semiconductor that exhibits robust doping with high carrier mobility over a wide range of carrier concentrations. Here we demonstrate that epitaxial thin films of the perovskite oxide NdxSr1−xSnO3 (SSO) do exactly this. Nd is used as a donor to successfully modulate the carrier concentration over nearly two orders of magnitude, from 3.7 × 1018 cm−3 to 2.0 × 1020 cm−3. Despite being grown on lattice-mismatched substrates and thus having relatively high structural disorder, SSO films exhibited the highest room-temperature mobility, ~70 cm2 V−1 s−1, among all known UWBG semiconductors in the range of carrier concentrations studied. The phonon-limited mobility is calculated from first principles and supplemented with a model to treat ionized impurity and Kondo scattering. This produces excellent agreement with experiment over a wide range of temperatures and carrier concentrations, and predicts the room-temperature phonon-limited mobility to be 76–99 cm2 V−1 s−1 depending on carrier concentration. This work establishes a perovskite oxide as an emerging UWBG semiconductor candidate with potential for applications in power electronics. Semiconductor research is undergoing transformative changes thanks to the discovery and development of novel materials. The authors disclose the role of electron-phonon interaction and impurity scattering in a novel ultrawide bandgap perovskite oxide, paving the way for new applications in high-power electronics. [ABSTRACT FROM AUTHOR]

We investigate lanthanum (La) as an n-type dopant in the strain-stabilized tetragonal phase of SrSnO3 grown on GdScO3 (110) using a radical-based hybrid molecular beam epitaxy approach. Fully coherent, epitaxial films with an atomically smooth film surface were obtained irrespective of doping density. By combining secondary ion mass spectroscopy and Hall measurements, we demonstrate that each La atom contributes one free electron to the film, confirming that it occupies the Sr site in SrSnO3 and that it is completely activated. Carrier density exceeding 1 × 1020 cm−3 was achieved in La-doped SrSnO3 films, which is in excellent agreement with the dopant-solubility limit predicted by density functional theory calculations. A record-high room-temperature mobility of 70 cm2 V−1 s−1 at 1 × 1020 cm−3 was obtained in a 12 nm La-doped SrSnO3 film, making this the thinnest perovskite oxide semiconductor with electron mobility exceeding 25 cm2 V−1 s−1 at room temperature. We discuss the structure-dopant-transport property relationships, providing essential knowledge for the design of electronic devices using these materials. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) ultra-high carrier densities are of considerable current research interest for novel plasmonic and high charge-gain devices. However, the highest 2D electron density obtained is thus far limited to 3 × 1014 cm-2 (½ electron/unit cell/interface) at GdTiO3/SrTiO3 interfaces, and is typically an order of magnitude lower at LaAlO3/SrTiO3 interfaces. We show from experiment and modeling that carrier densities much higher than expected based on resolution of the polar discontinuity at perovskite oxide heterojunctions can be achieved via band engineering. The SrTiO3 (8 u.c.)/NdTiO3 ( t u.c)/SrTiO3 (8 u.c.)/LSAT(001) heterostructure shows the expected electronic reconstruction behavior starting at t = 2 u.c., but then exhibits a higher carrier density regime at t ≥ 6 u.c. due to additional charge transfer from band alignment. [ABSTRACT FROM AUTHOR]

The article discusses that according to study of subtle effects on transport in semiconductors demands high-quality epitaxial structures with low defect density. By using hybrid MBE growth, phenomenological modeling, temperature-dependent transport measurements, and scanning superconducting quantum interference device imaging, insights can be derived.

The discovery and development of ultra-wide bandgap (UWBG) semiconductors is crucial to accelerate the adoption of renewable power sources. This necessitates an UWBG semiconductor that exhibits robust doping with high carrier mobility over a wide range of carrier concentrations. Here we demonstrate that epitaxial thin films of the perovskite oxide NdxSr1−xSnO3 (SSO) do exactly this. Nd is used as a donor to successfully modulate the carrier concentration over nearly two orders of magnitude, from 3.7 × 1018 cm−3 to 2.0 × 1020 cm−3. Despite being grown on lattice-mismatched substrates and thus having relatively high structural disorder, SSO films exhibited the highest room-temperature mobility, ~70 cm2 V−1 s−1, among all known UWBG semiconductors in the range of carrier concentrations studied. The phonon-limited mobility is calculated from first principles and supplemented with a model to treat ionized impurity and Kondo scattering. This produces excellent agreement with experiment over a wide range of temperatures and carrier concentrations, and predicts the room-temperature phonon-limited mobility to be 76–99 cm2 V−1 s−1 depending on carrier concentration. This work establishes a perovskite oxide as an emerging UWBG semiconductor candidate with potential for applications in power electronics. Semiconductor research is undergoing transformative changes thanks to the discovery and development of novel materials. The authors disclose the role of electron-phonon interaction and impurity scattering in a novel ultrawide bandgap perovskite oxide, paving the way for new applications in high-power electronics. [ABSTRACT FROM AUTHOR]

Through systematic control of the Nd concentration, we show that the carrier density of the two-dimensional electron gas (2DEG) in SrTiO3/NdTiO3/SrTiO3(001) can be modulated over a wide range. We also demonstrate that the NdTiO3 in heterojunctions without a SrTiO3 cap is degraded by oxygen absorption from air, resulting in the immobilization of donor electrons that could otherwise contribute to the 2DEG. This system is, thus, an ideal model to understand and control the insulator-to-metal transition in a 2DEG based on both environmental conditions and film-growth processing parameters. [ABSTRACT FROM AUTHOR]