High‐Performance Ultra‐Wide‐Bandgap CaSnO ₃ Metal‐Oxide‐Semiconductor Field‐Effect Transistors

Abstract 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 (CaSnO ₃ ) has the largest band gap of ≈4.7 eV, holding great promise for high‐power applications. However, the demonstration of CaSnO ₃ 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 CaSnO ₃ are demonstrated for the first time. The MOSFETs exhibit an on/off ratio exceeding 10 ⁸ , along with field‐effect mobility of 8.4 cm ² V ⁻¹ s ⁻¹ and on‐state current of 30 mA mm ⁻¹ . The high performance of the CaSnO ₃ 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 CaSnO ₃ in future high‐voltage power electronic technologies.