Electrical properties of pseudo-single-crystalline Ge films grown by Au-induced layer exchange crystallization at 250 °c

We study the electrical properties of pseudo-single-crystalline Ge (PSC-Ge) films grown by a Au-induced layer exchange crystallization method at 250 °C. By inserting the SiN_x layer between PSC-Ge and SiO₂, we initiatively suppress the influence of the Ge/SiO₂ interfacial defective layers, which have been reported in our previous works, on the electrical properties of the PSC-Ge layers. As a result, we can detect the influence of the ionized Au⁺ donors on the temperature-dependent hole concentration and Hall mobility. To further examine their electrical properties in detail, we also fabricate p-thin-film transistors (TFTs) with the PSC-Ge layer. Although the off-state leakage currents are suppressed by inserting the SiN_x layer, the value of on/off ratio remains poor (<10²). Even after the post-annealing at 400 °C for the TFTs, the on/off ratio is still poor (∼10²) because of the gate-induced drain leakage current although a nominal field effect mobility is enhanced up to ∼25 cm²/V s. Considering these features, we conclude that the Au contaminations into the PSC-Ge layer can affect the electrical properties and device performances despite a low-growth temperature of 250 °C. To achieve further high-performance p-TFTs, we have to suppress the Au contaminations into PSC-Ge during the Au-induced crystallization growth.