Characterisation of 200 mm GaAs and Ge substrate VCSELs for high-volume manufacturing

Emerging consumer applications of VCSEL arrays demand larger sizes and improved reliability. Significant wafer bow seen on a 150-mm GaAs-substrate wafer can impact fabrication, characterisation, and yields. It has been reported that Ge-substrates are drop-in replacements for GaAs, but also have additional benefits. We report on the spatial performance of identical 940 nm VCSELs, grown on both types of 200-mm substrate. Threshold current densities vary by 0.1μA/cm2 at the wafer centre, and a 0.78% and 0.59% decrease in centre-to-edge emission wavelengths for Ge and GaAs respectively. Results show a potential route to larger manufacturing volumes with lower costs per wafer.