High-Performance Ultra-Wide-Bandgap CaSnO₃ Metal-Oxide-Semiconductor Field-Effect Transistors

The increasing demand for high-voltage and high-power electronic applications has intensified the search for novel ultrawide bandgap (UWB) semiconductors. Alkaline earth stannates possess wide band gaps and exhibit the highest room-temperature electron mobilities among all perovskite oxides. Among this family, Calcium stannate (CaSnO₃) has the largest band gap of ≈4.7 eV, holding great promise for high-power applications. However, the demonstration of CaSnO₃ power electronic devices is so far limited. In this work, high-performance metal-oxide-semiconductor field-effect transistor (MOSFET) devices based on lanthanum (La)-doped CaSnO₃ are demonstrated for the first time. The MOSFETs exhibit an on/off ratio exceeding 10⁸, along with field-effect mobility of 8.4 cm² V⁻¹ s⁻¹ and on-state current of 30 mA mm⁻¹. The high performance of the CaSnO₃ MOSFET devices can be ascribed to the excellent metal-to-semiconductor contact resistance of 0.73 kΩ·µm. The devices also show great potential for harsh environment operations, as high-temperature operations up to 400 K are demonstrated. An off-state breakdown voltage of 1660 V is achieved, with a breakdown field of ∼8.3 MV cm⁻¹ among the highest reported for all UWB semiconductors. This work represents significant progress toward realizing the practical application of CaSnO₃ in future high-voltage power electronic technologies.