We demonstrate low-voltage waveguide silicon-germanium avalanche photodiodes (APDs) integrated with distributed Bragg reflectors (DBRs). The internal quantum efficiency is improved from 60% to 90% at 1550 nm assisted with DBRs while still achieving a 25 GHz bandwidth. A low breakdown voltage of 10 V and a gain bandwidth product of near 500 GHz are obtained. APDs with DBRs at a data rate of 64 Gb/s pulse amplitude modulation with four levels (PAM4) show a 30%–40% increase in optical modulation amplitude (OMA) compared to APDs with no DBR. A sensitivity of around $?13\mathrm{dBm}$ at a data rate of 64 Gb/s PAM4 and a bit error rate of $2.4\times {10}^{?4}$ is realized for APDs with DBRs, which improves the sensitivity by $～2\mathrm{dB}$ compared to APDs with no DBR.