P-GaN Gated AlGaN/GaN E-mode HFET Fabricated with Selective GaN Etching Process

An O₂ based selective GaN etching process was developed herein for use in p-GaN gated AlGaN/GaN heterojunction field-effect transistor fabrication, where precise control of the p-GaN etching was an important process step that determined the device characteristics. The p-GaN layer was etched by a two-step process: low damage BCl₃/Cl₂ plasma etching in conjunction with Cl₂/N₂/O₂ based selective etching. A high selectivity of 53:1 for the p-GaN:AlGaN was achieved by the Cl₂/N₂/O₂ plasma etching. The device fabricated by the optimized etching process exhibited excellent enhancement-mode characteristics, i.e., a threshold voltage of 2.45 V, a specific on-resistance of 5.55 mΩ·cm², an on/off ratio of ~10SUP9/SUP, and an off-state breakdown voltage of 1100 V.