AlGaInP/GaInAs/GaAs MODFET devices with self-aligned p+ -GaAs gate structure.

A self-aligned fabrication scheme of a novel AlGaInP/GaInAs/GaAs-MODFET device has been developed. Two characteristic features have been incorporated in the device structure: An AlGaInP barrier which provides a larger conduction band offset than the commonly used AlGaAs and a highly carbon-doped p-type GaAs gate structure which supports a very simple fabrication scheme. Using 1mym optical lithography we have fabricated first demonstrator devices with a current gain cut-off frequency of 60 GHz and a power gain cut-off frequency of 140 GHz. In addition, the devices show large gate-drain diode breakdown voltages in excess of 30 V and gate currents as low as 50 nA even at gatesource voltages of -5 V.