Poly-GeSn Junctionless Thin-Film Transistors on Insulators Fabricated at Low Temperatures via Pulsed Laser Annealing

High-performance polycrystalline GeSn (poly-GeSn) junctionless thin-film transistors (JL-TFTs) are proposed and fabricated at low process temperatures. Poly-GeSn thin films with a Sn fraction of 4.8% are prepared using cosputtering and pulsed laser annealing (PLA) techniques. The ultra-rapid nonequilibrium thermodynamic process with 25 ns PLA renders a good crystal GeSn thin film at a low temperature. The I-ON/I-OFF ratio increases by three orders of magnitude with GeSn channel thickness varying from 60 to 10 nm, suggesting that switch-off current is dominated by depletion width. A superior effective mobility of 54 cm(2) V-1 s(-1) is achieved for the JL-TFT with a 10 nm-thick GeSn film as a consequence of gate/channel interface passivation by oxygen plasma.