High-Mobility p-Channel Thin-Film Transistors Based on Polycrystalline GeSn

GeSn has gained significant interest as a material for next-generation electronic devices, including thin-film transistors (TFTs) because of its excellent electronic properties. In this study, high-quality polycrystalline GeSn thin films are fabricated on glass substrates and fabricated high-performance TFTs. A bilayer structure with modulated deposition temperatures simultaneously suppressed nucleation and promoted growth, thereby enabling the formation of large-grained GeSn layers. The sample exhibited high Hall hole mobility (230 cm² V⁻¹ s⁻¹) and low hole concentration (4.1 × 10¹⁷ cm⁻³), which are the best electrical properties for polycrystalline Ge-based thin films applicable for accumulation-mode TFTs. The fabricated TFTs demonstrated field-effect mobility of up to 250 cm² V⁻¹ s⁻¹. This value is not only the highest for a polycrystalline Ge-based TFT, but also the highest for a p-channel TFT fabricated in a low-temperature process (≤500 °C). Thus, this study represents an important step toward the realization of high-performance TFTs using GeSn, which is a significant achievement that can contribute to the next generation of electronics technologies.