Improvement of poly-Ge TFT characteristics by atomic hydrogen annealing

Ge thin film is expected as an active layer in a thin-film transistor (TFT) because the electron mobility of Ge is larger than that of Si. In this study, the crystallization of Ge thin film by soft X-ray irradiation and the improvement of interface property of poly-Ge/SiO₂ in poly-Ge TFT by atomic hydrogen annealing (AHA) are investigated for realization of high-performance poly-Ge TFT. The drain current (I_d) did not depend on the gate voltage (V_g) before AHA treatment. However, as the AHA treatment time increased, the I_d decreased and the I_d came to depend on V_g. The on/off ratio of 10 was obtained by AHA for 360 min. It is found that the defect density in poly-Ge film and at poly-Ge/SiO₂ interface can be reduced by AHA slightly.