Discovery of Energy‐Localized Trap States via Opto‐Electrical Spectroscopy in UWBG Perovskite La:SrSnO 3 FETs

Abstract

ABSTRACT Strontium stannate perovskite (SrSnO 3 ) is emerging as a promising material for next‐generation ultra‐wide bandgap (UWBG) semiconductors due to its high electron mobility and optical transparency. However, despite the critical importance of defect analysis to utilize La‐doped SrSnO 3 as a semiconductor channel material, the energy distribution of sub‐gap states has not yet been sufficiently elucidated under bias conditions. In this work, we fabricated La‐doped SrSnO 3 top‐gate metal‐oxide‐semiconductor field‐effect transistors (MOSFETs) and characterized them under multi‐wavelength light ranging from 300–900 nm, quantitatively extracting the trap density over a wide range of energy spectra. The transient decrease in transmittance observed at 400 nm correlates with subthreshold swing degradation, revealing deep donor‐like traps as the dominant trap states. Notably, despite the presence of traps, La‐doped SrSnO 3 exhibits excellent optical durability with minimal threshold voltage fluctuations under multi‐wavelength illumination. The resulting fabricated MOSFETs achieved a high on/off current ratio (∼10 11 ), showing competitive performance and stability compared to previously reported oxide semiconductors. This work establishes an analytical framework for precisely unveiling the trap‐dominated behavior of SrSnO 3 and proposes essential design guidelines for the development of high‐reliability power and optoelectronic devices based on next‐generation UWBG perovskite semiconductors.