We　prepare　top-emitting　850　nm　vertical-cavity　surface-emitting　laser　(VCSEL)　with　a　large　oxide-aperture　of　11　µm.　The　temperature-dependence　of　the　output　characteristics　such　as　optical　output　power,　threshold　current,　differential　resistance　and　small-signal　modulation　bandwidth　(f3dB)　are　investigated.　At　room　temperature,　the　VCSEL　achieves　a　maximum　optical　output　power　of　12.62　mA　and　a　maximum　f3dB　of　18.5　GHz.　With　the　increase　of　temperature,　the　thermal　rollover　current　and　the　maximum　optical　output　power　both　decrease.　When　the　temperature　rises　to　55　℃,　the　f3dB　of　the　device　remains　above　18　GHz.　Finally,　the　modulation　current　efficiency　factor　(MCEF)　at　different　temperatures　is　extracted　by　linear　fitting　of　the　f3dB　and　the　square　root　of　the　bias　current　above　the　threshold.　©　2024　SPIE.