2DEGs and FETs based on perovskite oxide semiconductor BaSnO3
- Date: Jun 23, 2023
- Time: 02:00 PM - 03:00 PM (Local Time Germany)
- Speaker: Kookrin Char
- Institute of Applied Physics, Dept. of Physics and Astronomy, Seoul National University
- Location: Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Saale)
- Room: Lecture Hall, B.1.11
Over the last several years we have found a systematic behavior at the polar perovskite oxide interface of LaInO3/BaSnO3. It includes the LaInO3 thickness dependence, the La-doping dependence, the effect of the substrates, the Ga-alloying effect in LaInO3, remote doping in BaSnO3, and the termination layer effect. Such systematic behavior can be explained by the “interface polarization” model, where the polarization discontinuity plus the conduction band offset near the interface creates the potential well necessary for 2DEG formation. We found the semiconductor physics, as simulated by Poisson-Schrodinger equation”, to be sufficient to explain all the experimental findings in a consistent way.
The “interface polarization”, created by the inversion symmetry breaking at the orthorhombic LaInO3 and the cubic BaSnO3 interface, is a unique property of LaInO3/BaSnO3 2DEG, when compared with other 2DEGs such as (AlGa)As/GaAs, (AlGa)N/GaN, and (MgZn)O/ZnO. The “interface polarization” plus the large conduction band offset generates unusually large drop in the conduction band of larger than 3 eV near the interface. This creates very narrow confinement of the large 2-dimensional carrier density and large Rashba-type spin-orbit coupling at the interface. We are currently working to elucidate its low temperature transport properties. However, the path towards higher mobility at low temperatures is currently limited by the high density defects in the BaSnO3 film, which results mainly from the cation vacancies including the threading dislocations. We expect the single crystal substrates of BaSnO3 or LaInO3 will make great contribution to low temperature science of this unique 2DEG.
Technologically, BaSnO3 perovskite oxide semiconductor system provides a new platform to put together many interesting properties of various perovskite oxides and create new functions that have not been possible before. In particular, we are working on integrating its unique 2DEGs and field effect to create field effect transistors (FETs) with new functions. It includes high power FETs using a new high-k perovskite gate oxide, ferroelectric FETs using a low coercive field ferroelectric perovskite oxide, and DUV-transparent FETs using BaSnO3’s wider bandgap sister SrSnO3.