SIMPLIFIED OHMIC AND SCHOTTKY CONTACT FORMATION FOR FIELD-EFFECT TRANSISTORS USING THE SINGLE-LAYER INTEGRATED METAL FIELD-EFFECT TRANSISTOR (SLIMFET) PROCESS

A new III-V semiconductor device fabrication process for GaAs-based fi eld effect transistors (FET) is presented which uses a single lithogra phic process and metal deposition step to form both the ohmic drain/so urce contacts and the Schottky gate contact concurrently, This single layer integrated metal FET (SLIMFET) process simplifies the fabricatio n process by eliminating an additional lithographic step for gate defi nition, a separate gate metallization step, and thermal annealing for ohmic contact formation. The SLIMFET process requires a FET structure which incorporates a compositionally graded InxGa1-xAs cap layer to fo rm low resistance, nonalloyed ohmic contacts using standard Schottky m etals, The SLIMFET process also uses a Si3N4 mask to provide selective removal of the InGaAs ohmic layers from the gate region prior to meta llization without requiring an additional lithographic step, GaAs MESF ET devices were fabricated using this new SLIMFET process which achiev ed DC and RF performance comparable to GaAs MESFET's fabricated by con ventional methods.