Electrical characteristics of metal–semiconductor–metal (MSM) varactors fabricated on In0.53Ga0.47As/InAs/In0.53Ga0.47As composite channel HEMT structure

Abstract

In this paper, we have fabricated and characterized metal–semiconductor–metal (MSM) varactors with gate lengths ranging from 120, 180, and 290 nm on In0.53Ga0.47As/InAs/In0.53Ga0.47As composite channel high electron mobility transistor structure. We applied the buried-Pt gate technology to study the electrical characteristics of the MSM varactors depending on the gate-to-channel distance. The fabricated MSM varactors exhibited a cutoff frequency of 185 GHz for annealed varactors and 174 GHz for non-annealed varactors with L g of 120 nm, respectively. Also, non-annealed MSM varactors show an excellent capacitance ratio (=C max/C min) of 5.1 with L g of 290 nm, this is because of the longer gate-to-channel distance compared to annealed MSM varactors. The figure of merit (FOM = f 0·C max/C min) of the MSM varactors, which represents the performance of the MSM varactors, shows 451 and 438 for non-annealed and annealed devices, respectively.