Deep-ultraviolet transparent conducting SrSnO₃ via heterostructure design

Ultra-wide-bandgap (UWBG) semiconducting oxides are becoming pivotal in sustainable technologies due to their promising applications in next-generation high-power electronics and deep-ultraviolet (DUV) optoelectronics. This entails the need for a UWBG semiconductor that can effectively accommodate robust doping with tunable carrier concentrations, and high electrical conductivity and mobility. Here, we employ a thin heterostructure comprising 4 nm SrSnO₃/19 nm La:SrSnO₃/GdScO₃ (110) grown by hybrid molecular beam epitaxy (MBE). We utilize the heterostructure design and apply electrostatic gating, which allows us to effectively separate electrons in SrSnO₃ from dopants and achieve phonon-limited transport behaviors in strain-stabilized tetragonal SrSnO₃. This leads to a modulation of carrier density from 10¹⁸ cm^-3 to 10²⁰ cm^-3, with room-temperature mobilities ranging from 40 to 140 cm²V^-1s^-1. The phonon-limited mobility, calculated from first principles, closely matches experimental results, suggesting that room-temperature mobility could be further increased with higher electron density. Additionally, our film exhibits 85% optical transparency at a 300 nm wavelength. These findings highlight the potential of the heterostructure design for transparent UWBG semiconductor applications, especially in deep-ultraviolet regime.