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.