Allford, Craig Philip  ORCID: https://orcid.org/0000-0002-3798-9014, Smith, A. R., Gillgrass, S. J., Jandu, G. M ORCID: https://orcid.org/0009-0006-0758-9817, Power, S. V., Albittar, N., Davies, J. I., Clark, A. and Smowton, P. M. ORCID: https://orcid.org/0000-0002-9105-4842
2026.
On-wafer characterisation of 1300 nm InAs quantum dot laser uniformity over 150 mm substrates.
Journal of Physics D: Applied Physics
59
, 335102.
10.1088/1361-6463/ae961f
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Abstract
We report wafer scale characterisation of O-band 150 mm InAs quantum dot (QD) edge-emitting lasers, using on-wafer measurements of etched-facet lasers. Threshold current, lasing wavelength, and spontaneous emission spectra were mapped across the wafer and compared with post-growth photoluminescence (PL) peak emission wavelength and full-width half-maximum (FWHM) to evaluate device performance and uniformity. Strong correlation is observed between the post-growth PL data and the on-wafer laser characteristics. Pearson correlation coefficients of 0.93 were calculated between both PL peak emission wavelength and peak lasing wavelength, and PL peak emission wavelength and peak spontaneous emission wavelength. A coefficient of 0.56 was found between PL FWHM and threshold current. Together, these indicate excellent fabrication uniformity and demonstrate that device performance is strongly correlated with variations in the epitaxial growth. The PL peak emission wavelength and FWHM were 1281.70 nm and 57.90 nm with standard deviations of 1.00 nm and 1.62 nm, respectively. The low fabrication variability enables a lasing yield of 98.2% (of lasers with thresholds below the maximum current used during characterisation of 1.5 A) for a population of 1152 devices with a 2000 μm cavity length. By combining on-wafer etched-facet measurements with post singulation measurements on both cleaved-facet lasers alongside gain and absorption measurements from the segmented-contact method, the etched-facet reflectivity at 6 mm from the wafers centre was extracted to be 0.074 ± 0.003. Additional investigation indicates that the sub-optimal etched-facet reflectivity is likely due primarily to off-vertical angled facets, measured at 81.8o relative to the wafer surface, which increases mirror losses, raising the threshold current and reducing yield for shorter cavity devices due to the higher gain requirement. Overall, the spatial uniformity of the facet reflectivity demonstrates that on-wafer etched-facet test structures provide a robust platform for diagnosing epitaxial and fabrication variations without the need for extensive wafer cleaving.
| Item Type: | Article |
|---|---|
| Date Type: | Publication |
| Status: | Published |
| Schools: | Schools > Physical, Chemical & Environmental Sciences |
| Publisher: | IOP Publishing |
| ISSN: | 0022-3727 |
| Date of First Compliant Deposit: | 13 August 2026 |
| Last Modified: | 06 Oct 2026 21:16 |
| URI: | https://orca.cardiff.ac.uk/id/eprint/188977 |
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