Flexible Microwave Single-Crystal Si TFTs with fmax of 5.5 GHz

Microwave thin-film transistors on flexible plastic substrate using single-crystal Si as active channel material are reported in this paper. By employing a new TFT design, a maximum oscillation frequency (f
_max
) of 5.5 GHz, the highest reported speed for any devices on flexible substrate, has been achieved with an associated cut-off frequency (f
_T
) of 600 MHz. A maximum value of transconductance g
_m
of 22.28 muS with a gate length of about 1.5 mum is measured. The degradation of g
_m
in large gate-length device due to poor Si/SiO interface is described.