4 Inch Sapphire Wafer, Al2O3 Single Crystal Sapphire Substrate, SSP DSP Polished Product Description: 4 inch sapphire wafer, single crystal Al₂O₃ substrate. C-plane (0001), SSP / DSP polished, epi-ready grade. Low TTV, ultra-smooth surface, high thermal & chemical stability. Widely used for GaN epitaxy, LED, optoelectronics and optical devices. Custom thickness, orientation and PSS available. Clean packaging, stable supply. Introduction of Sapphire Wafers: Sapphire wafer is a