Lateral large-grained low-temperature polycrystalline silicon-germanium thin-film transistors on glass substrates

Lateral large-grained (LLG) polycrystalline silicon_1-x germanium_x (poly-Si_1-xGe_x) thin-film transistors (TFTs) with x = 0, 0.05, 0.1, and 0.3 were fabricated on glass substrates using a maximum processing temperature of 550°C. Silicon dioxide (SiO₂) was used as the gate dielectric, and the performance of the TFTs was evaluated in terms of mobility and subthreshold swing value (s-value). The LLG poly-Si_1-xGe_x films were crystallized by a diode-pumped solid-state continuous-wave laser with a wavelength of 532 nm. It was observed that the performance of poly-Si_1-xGe_x TFTs degraded with increasing Ge concentration despite the increasing grain length of the poly-Si_1-xGe_x. The Ge-dependent degradation mechanism of poly-Si_1-x Ge_x TFTs is thought to be caused by the charge state at the poly-Si_1-xGe_x/gate-SiO₂ interface.