Effects of germane flow rate in electrical properties of a-SiGe:H films for ambipolar thin-film transistors

• As the GeH4 flow rate increases the content of oxygen decreases.
• GeH bonds show the highest value in a-SiGe:H films with GeH4 flow of 105 sccm.
• Films with GeH4 flow of 105 sccm show the highest activation energy.
• An optimum incorporation of germanium is obtained with GeH4 flow rate of 105 sccm.
• At 200 °C the optimum condition of the a-SiGe:H films remain with no changes.

In this work, the study of germane flow rate in electrical properties of a-SiGe:H films is presented. The a-SiGe:H films deposited by low frequency plasma-enhanced chemical vapor deposition at 300 °C were characterized by Fourier transform infrared spectroscopy, measurements of temperature dependence of conductivity and UV–visible spectroscopic ellipsometry. After finding the optimum germane flow rate conditions, a-SiGe:H films were deposited at 200 °C and analyzed. The use of a-SiGe:H films at 200 °C as active layer of low-temperature ambipolar thin-film transistors (TFTs) was demonstrated. The inverted staggered a-SiGe:H TFTs with Spin-On Glass as gate insulator were fabricated. These results suggest that there is an optimal Ge content in the a-SiGe:H films that improves its electrical properties.