A high-quality ZnTe and TeO2 (ZTO) composite is grown on an n-type silicon substrate, using a modified metal-assisted chemical vapor deposition method. Self-powered photodetector based on a ZnTe-TeO2 composite/Si heterojunction with ultra-broadband and high responsivity is obtained. The photosensitive detection performances of the ZTO composite/Si heterojunction photodetector are assessed using photoresponse spectrum. The photodetector shows ultra-broadband photoresponsivity from UV to NIR lights as ZnTe has a moderate, direct band gap of 2.26 eV, TeO2 has a wide band gap of 4.0 eV, and Si has a narrow band gap of 1.12 eV. Upon exposure to 850 nm light at a zero-bias voltage, the detector shows a high responsivity of 75 mA/W, detectivity of 1.4 x 10(13) cm Hz(1/2)/W, fast response and recovery properties with response and recovery times both below 0.61 s, respectively. The working mechanism is illustrated from the band energy diagram of ZnTe/Si heterojunction and the high transmittance of TeO2.