Improved oxide-implanted VCSELs utilising the tapered oxide layer are presented. The VCSELs exhibited similar static performance, but superior modulation bandwidth up to 13.2 GHz, compared with conventional blunt oxide VCSELs. The damping rate was reduced two times in the tapered oxide VCSEL and therefore enhanced the maximal modulation bandwidth. A very clean eye was demonstrated from the improved VCSEL with a rising time of 26 ps, falling time of 40 ps and jitter of less than 20 ps, operating at 10 Gbit/s with 6 mA bias and 6 dB extinction ratio. A comprehensive small signal measurement and analysis was conducted. Based on the equivalent circuit model, the extrinsic bandwidth limitation of the tapered oxide VCSELs was determined.