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As an inevitable existence in semiconductor heterostructures, interfacial states have a non-negligible impact on the performance of heterojunction-based optoelectronic devices. Here, we develop high-performance photodiodes based on heterointerface-engineered type II SnO 2 /boron-doped diamond (BDD) heterojunctions. We modulate the type of the interfacial states of SnO 2 /BDD heterojunctions by changing the partial pressure of oxygen during the process of SnO 2 deposition by RF magnetron sputtering. As a result, backward rectifying, Zener, and forward rectifying diodes are obtained. The diversity of the diode characteristics is related to the carrier tunneling and avalanche multiplication effects. In addition, the I–V curve of the Zener diode has a negative differential resistance precursor under UV light irradiation. The photogenerated holes in the forward rectifier diode are easily trapped at the heterointerface during transmission. Zener and forward rectifier diodes can output positive and negative photocurrents (i.e., binary photoresponse) under on/off periodic light illumination owing to photovoltaic and pyro-phototronic effects. These results reveal the potential of SnO 2 /BDD heterojunctions in the field of optical logic computing devices. • Three SnO 2 /BDD heterojunction photodiodes with different types of interfacial states were fabricated. • All three devices can achieve binary photoresponse output, but have diverse diode characteristics in the dark. • The photoresponse spectrum of the device with weak donor-type interfacial states can be broadened to visible band. • The binary photoresponse mechanism of three devices are explained by photovoltaic and pyro-phototronic effects. [ABSTRACT FROM AUTHOR]