0.13 /spl mu/m gate-length In/sub 0.52/Al/sub 0.48/As-In/sub 0.53/Ga/sub 0.47/As metamorphic HEMTs on GaAs substrate

InAlAs-InGaAs metamorphic high electron mobility transistors (MM-HEMTs) on GaAs substrates have shown remarkable performance improvement in terms of cut-off frequency (Dumka et al., 1999), power (Contrata and Iwata, 1999), and noise (Whelan et al., 2000). The metamorphic structure employs a thick metamorphic buffer layer between the GaAs substrate and the active device layer to relax the lattice mismatch strain. This enables a device designer to choose from a wide range of In compositions in the HEMT channel for engineering of the device performance according to the requirements. In addition, GaAs substrates are cheaper and easily available in larger sizes as compared to conventional InP substrates. The relatively mature processing technology on GaAs substrates, particularly the backside processing technology, makes the metamorphic structures even more attractive. In this work, we have fabricated 0.13 /spl mu/m gate-length In/sub 0.52/Al/sub 0.48/As-In/sub 0.53/Ga/sub 0.47/As metamorphic HEMTs on GaAs substrates. The DC and RF performance of the devices have been measured. The devices exhibit a record unity current gain cut-off frequency of 235 GHz. To the best of our knowledge, this is the best-reported cut-off frequency result on metamorphic material.