High-performance Ga/sub 0.51/In/sub 0.49/P/GaAs airbridge gate MISFET's grown by gas-source MBE

Ga/sub 0.51/In/sub 0.49/P/GaAs MISFET's, in which Ga/sub 0.51/In/sub 0.49/P insulating 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 the insulating layer. Wide and flat characteristics of g/sub m/, g/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 insulating layer thickness of 50 mn and 100 mm. Moreover, the maximum values of J/sub t/'s and f/sub max/'s for a 1-/spl mu/m gate length device both occurred when t was between 50 and 100 mn. 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 insulating layer thickness between 50 and 100 mn were very suitable for microwave high-power device applications.