Micron-scale FETs of fully epitaxial perovskite oxides using chemical etching

Abstract

Advent of high mobility perovskite oxide semiconductor BaSnO₃ (BSO) has enabled all-perovskite oxide heterostructures such as 2DEGs and FETs. To date all-perovskite oxide device demonstrations have been focused on finding and integrating the compatible perovskite dielectric oxides such as polar LaInO₃ and LaScO₃ and non-polar BaHfO₃ and SrHfO₃. For these demonstrations the length scale of BSO-based heterostructure devices has been about 100 µm, primarily due to the use of stencil masks for patterning. In order to further reduce the length scale, we employed a top-down approach using both photolithography and chemical etching techniques to pattern FETs made entirely of perovskite oxide materials: Ba_0.997La_0.003SnO₃ channel layer, degenerately doped Ba_0.96La_0.04SnO₃ contact layer, and SrHfO₃ gate oxide layer. FETs of 3 µm channel length were fabricated using hydrofluoric acid and aqua regia as etchants. The FET exhibits a mobility of 38.8 cm²/Vs, an on/off ratio of 5.06 × 10⁷, and a drain current density of 6.05 × 10⁻² mA/μm, consistent with our expectation. These findings demonstrate the feasibility of patterning BSO through photolithography and chemical etching while maintaining the subsequent epitaxial growth, suggesting that BSO can be employed in a broader range of applications as well as for more precise studies of its intrinsic properties.