Flexible thin-film transistors on biaxial- and uniaxial-strained Si and SiGe membranes

We report flexible thin-film transistors (TFTs) fabricated on single-crystal Si-based semiconductor membranes using Schottky source/drain contacts. Unstrained-Si, strained-Si/SiGe/Si and unstrained-Si0.8Ge0.2 alloy membranes were integrated on plastic substrates via transferring the top template layers from silicon-on-insulator (SOI) and silicon-germanium-on-insulator (SGOI) substrates. Biaxially tensile-strained Si/SiGe/Si is realized by allowing elastic strain sharing between Si and SiGe alloy. High current drive capability and high electron mobility are demonstrated on these membranes. Further enhancement of the source-to-drain current is exhibited by using mechanically introduced uniaxial strain to the flexible TFTs. We propose that the enhancement of current drive capability is attributed to both carrier mobility enhancement and Schottky barrier height modification due to strain.