Performance enhancement by using the n+-GaN cap layer and gate recess technology on the AlGaN/GaN HEMTs fabrication

In this study, we proposed the GaN HEMTs structure with a very high doping GaN layer (lx lO 19 cm'3) as a cap layer to reduce the contact resistance and knee voltage. However, this high doping cap layer should be removed before putting the Schottky gate metal. Therefore, in order to achieve the lower contact resistance and maintain the higher breakdown voltage, the selective gate recess dry etching was used to let the gate metal deposited on the surface of undoped AlGaN layer directly. After comparing the recessed and conventional non-recessed GaN HEMTs, a lower knee voltage, a higher current density, and a higher microwave output power density have been observed obviously in the recessed GaN HEMTs.