Impact of strain-induced bow on the performance of VCSELs on 150mm GaAs- and Ge-substrate wafers

Jack Baker; Sara Gillgrass; Tomas Peach; Craig P. Allford; J. Iwan Davies; Andrew D. Johnson; Andrew M. Joel; Sung Wook Lim; Samuel Shutts; Peter M. Smowton

doi:10.1117/12.2624492

25 May 2022 Impact of strain-induced bow on the performance of VCSELs on 150mm GaAs- and Ge-substrate wafers

Jack Baker, Sara Gillgrass, Tomas Peach, Craig P. Allford, J. Iwan Davies, Andrew D. Johnson, Andrew M. Joel, Sung Wook Lim, Samuel Shutts, Peter M. Smowton

Author Affiliations +

Proceedings Volume PC12141, Semiconductor Lasers and Laser Dynamics X; PC1214108 (2022) https://doi.org/10.1117/12.2624492
Event: SPIE Photonics Europe, 2022, Strasbourg, France

Abstract

The strain-induced wafer bow for VCSEL epitaxial structures grown on GaAs substrates is measured and compared to that of Ge substrates. We find that the ~ 160 μm height difference between the centre and edge of a GaAs wafer results in a significant temperature gradient and hence has a large effect on oxidation rate in the high-Al layer in the top DBR of the epi-structure. We measure a resultant centre-to-edge variation in oxidation length of ~ 3 μm for a GaAs wafer. We assess the contributions of wafer bow and epi-layer non-uniformity, as well as temperature variation in the furnace, and find that the effect of the bow dominates. We employ a Very Quick Fabrication (VQF) method to rapidly produce oxide confined VCSELs across a 150 mm GaAs substrate wafer to assess the impact on device performance. By measuring threshold current density between 20 and 70 ℃, we find ~ 25 ℃ variation in the temperature corresponding to the alignment of the spectral peak of gain with the cavity resonance wavelength. However, we still find that the threshold current density at zero detuning, is lower for edge devices, which we attribute to material variation. We disentangle the different contributions to device performance to isolate the effect of material variation. We compare this remaining spatial non-uniformity to that of VCSELs grown on Ge substrates.

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Jack Baker, Sara Gillgrass, Tomas Peach, Craig P. Allford, J. Iwan Davies, Andrew D. Johnson, Andrew M. Joel, Sung Wook Lim, Samuel Shutts, and Peter M. Smowton "Impact of strain-induced bow on the performance of VCSELs on 150mm GaAs- and Ge-substrate wafers", Proc. SPIE PC12141, Semiconductor Lasers and Laser Dynamics X, PC1214108 (25 May 2022); https://doi.org/10.1117/12.2624492

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KEYWORDS

Semiconducting wafers

Vertical cavity surface emitting lasers

Gallium arsenide

Germanium

Oxidation

Oxides

Manufacturing

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