AlGaInP/GaInAs/GaAs MODFET devices - candidates for optoelectronic integrated circuits

Modulation doped field effect transistors (MODFETs) with a phigh+-GaAs gate structure were fabricated from AlGaInP/GaInAs/GaAs heterostructures for the first time. Self-aligned devices with a gate length of 0.7 mym exhibit drain currents of 330 mA mmhigh-1, transconductances of 200 mS mmhigh-1 and very small gate currents below 50 nA even at gate-source voltages of - 5 V. Furthermore, large gate-drain diode breakdown voltages in excess of 30 V are observed. Short gatelength devices (0.3 mym) show a good r.f. performance with a current gain cut-off frequency of 60 GHz and a maximum frequency of oscillation of 140 GHz.