Recessed gate processing for GaN/AlGaN-HEMTs
A dry etch process based on Cl2/SF6 has been developed to selectively remove GaN over AlGaN for the fabrication of recessed gate GaN/AlGaN HEMTs. Using this etching process recessed and non-recessed FETs were fabricated side by side on the same wafer to provide a fair comparision of data. Recessed gate FETs with a gatelength of 0.15µm show cutoff frequencies of 83 and more than 200 GHz for fT and fmax, respectively. Furthermore, gate-drain breakdown as high as 84V has been obtained which is more than twice as much compared to their non-recessed counterparts.