Varactor diodes based on an AlGaN/GaN HEMT layer structure

We report the fabrication and characterization of MSM diodes on an AlGaN/GaN HEMT layer system for varactor applications. Device fabrication uses standard HEMT processing steps, allowing an integration in HEMT circuits without the need of sophisticated growth or etching techniques. The C/sub MAX//C/sub MIN/ ratio can be tuned by electrode geometry in contrast to conventional varactor diode concepts. Capacitance-voltage measurements exhibit C/sub MAX//C/sub MIN/ ratios up to 100. These results exceed best values for published heterostructure varactor diodes. Fabrication of AlGaN/GaN HEMTs on the same layer system with identical technology prove the potential for monolithic integration.