III-nitride transistors with capacitively coupled contacts

AlGaN/GaN heterostructure field-effect transistor design using capacitively coupled contacts ((CHFET)-H-3) is presented. Insulated-gate [C-3 metal-oxide-semiconductor HFET ((CMOSHFET)-M-3)] has also been realized. The capacitively coupled source, gate, and drain of C-3 device do not require annealed Ohmic contacts and can be fabricated using gate alignment-free technology. For typical AlGaN/GaN heterostructures, the equivalent contact resistance of C-3 transistors is below 0.6 Omega mm. In rf-control applications, the (CHFET)-H-3 and especially the (CMOSHFET)-M-3 have much higher operating rf powers as compared to HFETs. C-3 design is instrumental for studying the two-dimensional electron gas transport in other wide band gap heterostructures such as AlN/GaN, diamond, etc., where Ohmic contact fabrication is difficult. (c) 2006 American Institute of Physics.