0.32µm gate length InP-channel MODFETS with f_t above 90 GHz

The fabrication and characterisation of high performance InAlAs/InP modulation-doped field-effect transistors (MODFETs) with 0.32µm 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_m as high as 805mS/mm and unity current-gain cut-off frequency f_t, as high as 92GHz obtained for these devices at a drain-to-source voltage V_ds of 2 V are attributed to the low parasitics. Also, these devices exhibited an f_t, of at least 75 GHz up to a V_ds of 4 V.