InGaN-Channel Heterostructure Field Effect Transistor With Double Recessed Gate for Improved RF Performance

We propose a new approach for fabrication of reliable, high breakdown voltage InGaN-channel transistors for next generation radars and communications systems. Double recessed gate design enabled to increase breakdown voltage, alleviate non-ideal effects, and suppressing current instabilities and dispersion effects in GaAs-based HEMTs. However, no robust high performance double recessed gate GaN-based HFET technology has been developed. We propose to develop new epitaxial layer design with ternary (InGaN) and quaternary (AlInGaN) stop etch layers for double recess device fabrication. We already demonstrated significant improvement in the RF performance of AlGaN/InGaN/AlGaN/GaN-based HFETs with recessed gate design. We used our novel Migration Enhanced MOCVD (MEMOCVDTM) deposition technique to incorporate a very thin (2 nm) InGaN layer into AlGaN barrier. We propose to combine this approach with our novel AlGaN/AlInGaN/InGaN/GaN based Triple HFET (THFET) design. Quaternary AlInGaN cap layer grown over InGaN channel will be used as a second (lower) stop etch layer for RIE etch. We will recess both source and drain ohmic contacts and will fabricate them on In-containing AlInGaN cap layer for reduced contact resistance. The benefits of the proposed design are higher breakdown voltage without introduction of field plate design (which degrades high-frequency performance) and suppression of current dispersion.