Wan, ZeyuZeyuWanYang, Yun ChengYun ChengYangChen, Wei HsinWei HsinChenChiu, Chih ChuanChih ChuanChiuZhao, YunlongYunlongZhaoFeifel, MarkusMarkusFeifelChrostowski, LukasLukasChrostowskiLackner, DavidDavidLacknerCHAO-HSIN WUXia, GuangruiGuangruiXia2024-03-072024-03-072024-02-121094-4087https://scholars.lib.ntu.edu.tw/handle/123456789/640574This research successfully developed an independent Ge-based VCSEL epitaxy and fabrication technology route, which set the stage for integrating AlGaAs-based semiconductor devices on bulk Ge substrates. This is the second successful Ge-based VCSEL technology reported worldwide and the first Ge-based VCSEL technology with key details disclosed, including Ge substrate specification, transition layer structure and composition, and fabrication process. Compared with the GaAs counterparts, after epitaxy optimization, the Ge-based VCSEL wafer has a 40% lower surface root-mean-square roughness and 72% lower average bow-warp. After device fabrication, the Ge-based VCSEL has a 10% lower threshold current density and 19% higher maximum optical differential efficiency than the GaAs-based VCSEL.enjournal article10.1364/OE.513997384393602-s2.0-85185261455https://api.elsevier.com/content/abstract/scopus_id/85185261455