Magnetorheological electro-Fenton composite polishing technology is a new processing method that uses the synergy of electro-Fenton reaction and magnetorheological polishing flexible mechanical removal to achieve high efficiency polishing of GaN. To reveal the effect of different electro-Fenton parameters on the generation of hydroxyl radicals (⋅OH) and to explore the optimal process parameters for the magnetorheological electro-Fenton composite polishing of single crystal GaN clusters, methyl orange degradation experiments were designed by the Box-Behnken design (BBD) method. The effects of three electro-Fenton parameters, namely H₂O₂ concentration, Fe-C concentration and pH value, on the variation pattern of hydroxyl radical (⋅OH) concentration were investigated. The prediction function of the degradation rate of methyl orange under the electro-Fenton system was constructed and the reliability of the prediction function was verified, so that the electro-Fenton parameters could be optimised. The effect of different polishing process parameters (abrasive particle size, concentration and polishing time) on the surface quality of GaN wafers is investigated with the objective of optimising the polishing process parameters. The results showed that there was a maximum value of 94.3% degradation of methyl orange at a concentration of 4.8 wt% H₂O₂, 3.4 wt% Fe-C and pH=3.3. The GaN was polished for 1 h with an abrasive type of diamond, an abrasive grain size of 500 nm and an abrasive concentration of 3 wt%. Magnetorheological electro-Fenton compound polishing was able to reduce the surface roughness from Ra 15 nm to Ra 1.2 nm with a material removal rate of up to 10.79 μm/h.

Gallium nitride (GaN),Magnetorheological polishing,Electro-Fenton,Hydroxyl radicals,Response surface methodology