0.32 mu m gate length InP-channel MODFETs with ft above 90 GHz

The fabrication and characterisation of high performance InAlAs/InP modulation-doped field-effect transistors (MODFETs) with 0.32 mu m gate lengths are reported. Devices have been fabricated on two different delta-doped heterostructures with one having an extra delta-doping plane just below the cap layer. The extra doping resulted in devices with lower source and drain parasitic resistances. Extrinsic DC transconductances g_mas high as 805 mS/mm and unity current-gain cutoff frequency f_t as high as 92 GHz obtained for these devices at a drain-to-source voltage V_ds of 2V are attributed to the low parasitics. Also, the devices exhibited an f_t of at least 75 GHz up to a V_ds of 4 V.