InGaAs/InAlAs HEMTs with extremely low source and drain resistances
The performance of InP based InAlAs/InGaAs high electron mobility transistors (HEMTs) is often limited by large parasitic source and drain resistances, caused by high contact and sheet resistances in the access regions. The authors demonstrate that a highly conductive cap layer can be seen as an extension of the ohmic contact if a sufficient tunnelling current between cap layer and channel can be achieved. The significantly reduced source and drain resistances lead to excellent DC and RF characteristics with an extrinsic transconductance of 1150 mS/mm and a current cutoff frequency of 206 GHz (L/sub G/=150 nm).