Selective undercut etching for ultra narrow mesa structure in vertical InGaAs channel MISFET

It is important for shrinking the mesa width of a channel region in a vertical InGaAs channel MISFET for carrying out high-speed operation and for obtaining a steep sub-threshold slope. Therefore, we introduced selective undercut etching after the dry etching of the mesa structure. In the fabricated device with 60-nm-long channel, the channel mesa width became 15 nm. The maximum drain current density at V_ds = 0.75 V and V_g = 1.5 V was 1.1 A/mm and the maximum transconductance at V_ds = 0.75 V and V_g = 0 V was 530 mS/mm.