For the first time, heterogeneous integration of InGaAs/InAlAs single-photon avalanche diodes (SPADs) with Si photonics was realized and demonstrated through a low temperature die-to-die bonding technique. Together with the adoption of a triple-mesa structure in SPADs which not only avoids the surface exposure to the high electric field but also alleviate the electric field crowding at mesa edges, our integrated SPADs exhibit high single-photon detection efficiency (SPDE) of ~22% and low dark count rate (DCR) of 8.6 ×10⁵ Hz, which are among the best performance reported for InGaAs/InAlAs SPADs, and are approaching that of InGaAs/InP SPADs. High device yield and performance uniformity were also achieved.