A new power MISFET with undoped GaAs-Al0.3Ga0.7As superlattice gate “insulator” and buffer structure has been fabricated successfully. The superlattice gate “insulator” exhibits a much higher gate breakdown voltage( >35V) with very low prebreakdown leakage current and a lower gate capacitance (C ). Due to the existence of gate “insulator”, a higher carrier concentration can be employed in the active channel which improves the output drain current capability and transconductance. If the gate length is reduced to 1 um, a higher transconductance up to 330 mS/mm can be expected.
The insertion of superlattice buffer structure, between active channel and buffer layer offers an excellent carrier confinement barrier and gives an interface degraded region smaller than 40A. In addition, the superlattice buffer structure can getter greatly deep level impurities and defects from substrate or buffer layer. In summary, the proposed MISFET structure is suitable for high power, high frequency and low noise applications.