Abstract

We report on the fabrication of 50nm metamorphic GaAsHEMTs with a very high yield and uniformity as determined by DC characterisation, and excellent RF figures of merit. The T-gates were realised using a combination of high resolution electron beam lithography using a bi-layer (rather than the usual tri-layer) of PMMA/Co-polymer and a selective wet etch to form the gate recess. With an electrical yield greater than 95 %, the devices displayed a threshold voltage of -0.445V with a standard deviation of ± 0.005V. The transconductance of the devices was 1169mS/mm 83 mS/mm and demonstrated a cut-off frequency, fT of 330GHz.