[{"key":"dc.contributor.author","value":"Wan, Zeyu","language":null},{"key":"dc.date.accessioned","value":"2026-04-01T22:12:22Z","language":null},{"key":"dc.date.available","value":"2026-04-01T22:12:22Z","language":null},{"key":"dc.date.issued","value":"2026","language":"en"},{"key":"dc.identifier.uri","value":"http:\/\/hdl.handle.net\/2429\/93904","language":null},{"key":"dc.description.abstract","value":"Germanium (Ge) substrates offer a viable path to scale Vertical-Cavity Surface-Emitting Lasers (VCSELs) to 8\u2019\u2019 and 12\u2019\u2019 wafers. Compared with GaAs wafers, Ge reduces bow\/warp and is compatible with silicon complementary metal\u2013oxide\u2013semiconductor manufacturing. Although Ge-based VCSELs with high performance were reported in 2021, process details were undisclosed, leaving the open literature without a reproducible framework or understanding of yield and uniformity mechanisms on Ge. \r\nThis thesis develops an independent Ge-based VCSEL technology route, benchmarks it against GaAs-based controls, and systematically studies performance variation.\r\nFirst, a half-VCSEL structure comprising n-type distributed Bragg reflectors (n-DBRs) and multiple quantum wells (MQWs) validated the engineered Ge substrate consisting of GaAs\/InGaAs\/InGaP layers grown on a 6\u00b0 offcut Ge substrate. The half-VCSEL epitaxy validated suppression of anti-phase domains and achieved a surface roughness of 0.84 nm. Photoluminescence (PL) from the MQWs showed peak intensities comparable to GaAs-based controls at 200 mW excitation.\r\nSecond, a full VCSEL structure on engineered Ge substrates exhibited comparable epitaxial quality and better surfaces than GaAs-based counterparts, with a 72% reduction in wafer bow\/warp and a 40% reduction in roughness. Fabricated Ge-based VCSELs demonstrated successful lasing with static performance comparable to GaAs-based devices; the best Ge-based devices exhibited a 19% higher differential efficiency.\r\nDespite improved flatness and roughness, Ge-based VCSELs exhibited lower yield and larger performance variation than GaAs-based counterparts. A power-dependent PL study on half-VCSELs without a p-DBR found a 1.26 nm thermal redshift, implicating defect-related non-radiative recombination heating and revealing a p-DBR masking effect: thick p-DBRs conceal strain in the buried MQW. An isolated MQWs+ structure grown on engineered Ge substrates revealed 70\u201385 MPa residual stress and a dislocation-induced crosshatch pattern, causing a five- to eleven-fold reduction in PL intensity and loss of X-ray diffraction Pendell\u00f6sung fringes. This confirms the p-DBR masking effect and shows the importance of MQW epitaxial quality.\r\nOverall, this thesis establishes an independently developed Ge-based VCSEL process with details disclosed and provides one of the first systematic studies of variation and yield in Ge-based VCSELs, identifying accumulated stress and defect control in the buried MQWs as essential for improving yield, uniformity, and reliability.","language":"en"},{"key":"dc.language.iso","value":"eng","language":"en"},{"key":"dc.publisher","value":"University of British Columbia","language":"en"},{"key":"dc.rights","value":"Attribution-NonCommercial-NoDerivatives 4.0 International","language":"*"},{"key":"dc.rights.uri","value":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/","language":"*"},{"key":"dc.title","value":"Monolithic integration of 940 nm vertical-cavity surface-emitting lasers on bulk Germanium substrate : a comparative study and systematic diagnosis","language":"en"},{"key":"dc.type","value":"Text","language":"en"},{"key":"dc.degree.name","value":"Doctor of Philosophy - PhD","language":"en"},{"key":"dc.degree.discipline","value":"Materials Engineering","language":"en"},{"key":"dc.degree.grantor","value":"University of British Columbia","language":"en"},{"key":"dc.contributor.supervisor","value":"Xia, Guangrui","language":null},{"key":"dc.date.graduation","value":"2026-05","language":"en"},{"key":"dc.type.text","value":"Thesis\/Dissertation","language":"en"},{"key":"dc.description.affiliation","value":"Applied Science, Faculty of","language":"en"},{"key":"dc.description.affiliation","value":"Materials Engineering, Department of","language":"en"},{"key":"dc.degree.campus","value":"UBCV","language":"en"},{"key":"dc.description.scholarlevel","value":"Graduate","language":"en"}]