GaN HEMT ohmic metal electrode and preparation method thereof

The invention discloses a GaN HEMT (High Electron Mobility Transistor) ohmic metal electrode and a preparation method thereof. The preparation method comprises the following specific steps: step 1, sequentially cleaning a GaN epitaxial wafer by adopting NMP (N-Methyl Pyrrolidone), ammonia water and diluted HCl, and then flushing and spin-drying; step 2, coating a negative photoresist on the wafer, exposing and developing so as to define a source-drain ohmic metal pattern area on the GaN epitaxial wafer; step 3, carrying out incomplete etching on the AlGaN barrier layer by adopting an ICP atomic layer etching technology; 4, the etched wafer is cleaned and spin-dried, and then four layers of ohmic metal are manufactured; step 5, removing redundant metal outside the ohmic metal area by using a blue film gold tearing technology, and removing the photoresist to obtain a source metal electrode and a drain metal electrode; and step 6, placing the wafer in a high-temperature annealing furnace for annealing to obtain