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Next-generation VCSEL
Replacing the upper DBR of the active layer with a diffraction grating significantly enhances VCSEL performance. This innovative approach employs a high-refractive index sub-wavelength diffraction grating (HCG), resulting in an HCG-VCSEL. As a next-generation VCSEL, it not only reduces the thickness of the epi layer but also incorporates a polarization control function, garnering considerable attention in the field.
This SEM image showcases HCG processing on a ø6-inch GaAs wafer patterned with a resist mask. Etching was performed on HCG samples with a depth of 340 nm and GaAs (190 nm) / Air-gap (275 nm) intervals. The etching process achieved a rate of approximately 50 nm/min with a selectivity of about 5:1 relative to the resist mask. The result was a vertical, smooth sidewall with excellent in-plane uniformity of ±3.3% across the ø6-inch wafer.