Field effect transistors for power applications in millimetre wave range

The main requirements for power devices in the millimetre wave range are high values of current gain cut-off frequency, maximum current density and breakdown voltages. Among the various kinds of field effect transistors available, AlInAs-InGaAs MODFETs on an InP substrate have the greatest potential, in term of speed and drain current capabilities. Up to very recently, the main problem remained the low values of breakdown voltage, but recent improvements resulting from a better recessed zone configuration may solve this problem fully. On the other hand, metamorphic HEMT structures on GaAs substrates can constitute a better candidate in term of current density and voltage capabilities, having in mind the availability of low cost GaAs substrates. Also for this frequency range, MESFET or HEMT structures using large band gap materials such as SiC or GaN can constitute a very promising solution due to the low values of carrier mobility.