The relationship between the depth of the subsurface damage (SSD) and the size of the diamond abrasive used for mechanical polishing (MP) of GaN substrates was investigated in detail. GaN is categorized as a hard, brittle material, and material removal in MP proceeds principally to the fracture of GaN crystals. Atomic force microscopy and cathodoluminescence imaging revealed that the mechanical processing generated surface scratches and SSD. The SSD depth reduced as the diamond abrasive size reduced. A comparison of the relationship between the SSD depth and the diamond abrasive size used in the MP of GaN with the same relationship for typical brittle materials such as glass substrates suggests that the MP of GaN substrates proceeds via the same mechanism as glass.
• The detailed study on subsurface damage (SSD) generation by mechanical polishing (MP) was conducted for GaN substrate for the first time.
• Proves that the MP generated surface scratches and SSD were provided.
• A comparison in the mechanism of SSD generation between GaN and glass, typical brittle material, were also conducted.
• MP of GaN substrates was found to proceed via the same mechanism as glass.
Source: Applied Surface Science