Method for fabricating a recessed ohmic contact for a PHEMT structure

A method for reducing on-state resistance of a pseudomorphic high electron mobility transistor structure, said pseudomorphic high electron mobility transistor structure comprising a buffer layer, a conductive channel layer situated on said buffer layer, a spacer layer situated on said conductive channel layer, a first etch stop layer situated on said conductive channel layer, a lightly doped layer situated on said first etch stop layer, a second etch stop layer situated on said lightly doped layer, and a heavily doped layer situated on said second etch stop layer, said method comprising steps of:

• etching, to a depth of between 400.0 Angstroms and 1000.0 Angstroms, a recess in a source/drain contact region of said pseudomorphic high electron mobility transistor structure that extends through said heavily doped layer, said second etch stop layer, said lightly doped layer, and said first etch stop layer and exposes a top surface of said spacer layer;
• depositing at least one metal layer on said spacer layer in said recess;
• and
• performing a heating process to cause said at least one metal layer to bond to said conductive channel layer, thereby forming a recessed ohmic contact;
• wherein said recessed ohmic contact reduces said on-state resistance of said pseudomorphic high electron mobility transistor structure.