Fabrication and simulation of high-power high-speed Ga/sub 0.51/In/sub 0.49/P/GaAs airbridge gate MISFET´s grown by GSMBE

Ga/sub 0.51/In/sub 0.49/P/GaAs MISFET´s, where a Ga/sub 0.51/In/sub 0.49/P insulator layer was inserted between the gate metal and the channel layer, were compared with MESFET´s experimentally and theoretically in terms of dc and microwave performance. Devices performance were evaluated by varying the thickness of insulating layer. Wide and flat characteristics of g/sub m/, f/sub t/ and f/sub max/ versus drain current (or gate voltage) together with a high maximum current density (above 610 mA/mm) were achieved for devices with insulator thicknesses (t) of 50 nm and 100 nm. Moreover, the maximum values of f/sub t/´s and f/sub max/´s for a 1 pm gate length device both occurred when t was between 50 nm and 100 nm. We also observed that parasitic capacitances and gate leakage currents were minimized by using the airbridge gate structure, and thus high frequency and breakdown characteristics were greatly improved. These results demonstrate that Ga/sub 0.51/In/sub 0.49/P/GaAs airbridge gate MISFET´s with insulator thickness between 50 nm and 100 nm were very suitable for microwave high power device applications.