The　4.2%　mismatch　at　the　Si/Ge　interface　has　a　significant　impact　on　Si/Ge　photodetectors.　However,　few　researchers　have　attempted　to　determine　the　major　noise　source　or　study　the　effects　of　the　Si/Ge　interface　on　the　dark　current,　the　responsivity　and　the　3-dB　bandwidth　of　these　devices.　In　this　letter,　we　found　that　the　dark　current　was　dominated　by　generation-recombination　processes　that　were　enhanced　by　trap-assisted-tunneling　around　the　interface　below　220　K,　with　a　characteristic　tunneling　energy　of　E-00　=　14　meV　corresponding　to　an　effective　mass　of　m*　=　18m(0).　This　behavior　can　be　explained　by　the　rise　in　the　heavy-hole　band　caused　by　the　compressive　strain　on　the　Ge　layer.　When　the　temperature　increased　above　240　K,　Shockley-Read-Hall　recombination　was　clearly　observed　and　believed　to　be　dominant.　The　responsivity,　the　collection　efficiency　and　the　absorption　efficiency　were　all　extracted　at　850　nm,　1310　nm,　and　1550　nm.　The　absorption　coefficient　around　the　interface　was　found　to　be　lower　than　that　of　the　bulk　material.　In　addition,　comparison　of　the　measured　3-dB　frequency　(similar　to　20.6　GHz　@　-0.5　V)　with　the　theoretical　value　(similar　to　29.37　GHz)　indicated　that　defects　have　little　effect　on　the　bandwidth　at　high　frequencies.