Consumer applications of VCSEL arrays demand larger sizes and improved reliability. Ge-substrates are drop-in replacements for GaAs, whilst offering additional benefits. Thinner Ge-substrates are readily available due to photovoltaic supply chains, offering a cheaper cost per wafer. We report on device performance of identical 940-nm VCSELs, grown on 675µm, 500µm and 225µm thick Ge-substrates. Threshold current densities vary by less than 10μA/µm2 and 36μA/µm2 at the wafer centre between 675µm and, 500µm and 225µm respectively. A 3nm wavelength shift with decreasing substrate thickness is also observed. Results show a potential route to larger manufacturing volumes with lower cost per wafer.
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