New processing methods for n-GaAs field effect transistors using neutralisation of shallow donors by hydrogen and dissociation process by UV light

An original process is presented for fabricating GaAs field effect transistors. This process is based on the neutralisation of shallow donors by atomic hydrogen diffused in a highly doped and thin GaAs:Si epilayer and on the reactivation of particular hydrogenated zones by exposure to UV light. Using these new techniques, we have studied the performance of field effect transistors when their source and drain access resistances are gradually decreased. Initial hydrogenated FETs show very encouraging characteristics. For a gate length of 0.3 μm, typical transconductances are 800 mS/mm with cutoff frequencies >70 GHz